What are the strengths and weaknesses of attempts to describe Nirvana in scripture? How can we evaluate which description of nirvana is accurate? Also what problems does King Millinda point out about nirvana in his 80th dilemma?
The Pali suttas provide accurate descriptions of Nirvana, such as the 'destruction of craving' (Dhammapada 154; MN 37); 'visible here-&amp;-now destruction of greed, hatred &amp; delusion' (AN 3.55; SN 45.7); 'supreme happiness' (Dhammapada 203); and 'Simile of the Ocean'. 

Therefore, the description by Nâgasena given to King Millinda in his 80th dilemma should be compared to the Pali suttas to test its accuracy. 

That Nagasena offered a very lengthy answer shows he did not really have a "dilemma" &amp; spoke falsely, when he said: 'Nirvâna, O king, has nothing similar to it. By no metaphor, or explanation, or reason, or argument can its form, or figure, or duration, or measure be made clear.'

These links might help: Nibbana For Everyone &amp; Bhikkhu Pesala What Is Nibbāna?

Have you bothered to read the text or are you a university student looking for an easy answer? 


  'O happy word, Nâgasena! Speak then, quickly, that I may have an
  explanation of even one point in the characteristics of Nirvâna.
  Appease the fever of my heart. Allay it by the cool sweet breezes of
  your words!'
  
  'There is one quality of the lotus, O king, inherent in Nirvâna, and
  two qualities of water, and three of medicine, and four of the ocean,
  and five of food, and ten of space, and three of the wish-conferring
  gem, and three of red sandal wood, and three of the froth of ghee, and
  five of a mountain peak.'
  
  
  'Venerable Nâgasena, that one quality of the lotus which you said was inherent in Nirvâna,--which is that?'
  
  
  'As the lotus, O king, is untarnished by the water 3, so is Nirvâna
  untarnished by any evil dispositions. This is the one quality of the
  lotus inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those two qualities of water which you said were inherent in Nirvâna,--which are they?'
  
  
  'As water, O king, is cool and assuages heat, so also is Nirvâna
  cool, and assuages the fever arising from all evil dispositions.
  This is the first quality of water inherent in Nirvâna. And again, O
  king, as water allays the thirst of men and beasts when they are
  exhausted and anxious, craving for drink, and tormented by thirst, so
  does Nirvâna allay the thirst of the craving after lusts, the
  craving after future life, and the craving after worldly prosperity
  . This is the second quality of water inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those three qualities of medicine, which you said were inherent in Nirvâna,--which are they?'
  
  
  'As medicine, O king, is the refuge of beings tormented by poison, so
  is Nirvâna the refuge of beings tormented with the poison of evil
  dispositions. This is the first quality of medicine inherent in
  Nirvâna. And again, O king, as medicine puts an end to diseases, so
  does Nirvâna put an end to griefs. This is the second quality of
  medicine inherent in Nirvâna. And again, O king, as medicine is
  ambrosia, so also is Nirvâna ambrosia. This is the third quality
  of medicine inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those four qualities of the ocean which you said were inherent in Nirvâna,--which are they?'
  
  
  'As the ocean, O king, is free from (empty of) corpses, so also is
  Nirvâna free from (empty of) the dead bodies of all evil
  dispositions. This, O king, is the first quality of the ocean
  inherent in Nirvâna. And again, O king, as the ocean is mighty and
  boundless, and fills not with all the rivers that flow in to it; so is
  Nirvâna mighty and boundless, and fills not with all beings (who
  enter in to it). This is the second quality of the ocean inherent in
  Nirvâna. And again, O king, as the ocean is the abode of mighty
  creatures, so is Nirvâna the abode of great men--Arahats, in whom the
  Great Evils and all stains have been destroyed, endowed with
  power, masters of themselves. This is the third quality of the ocean
  inherent in Nirvâna. And again, O king, as the ocean is all in
  blossom, as it were, with the innumerable and various and fine flowers
  of the ripple of its waves, so is Nirvâna all in blossom, as it were,
  with the innumerable and various and fine flowers of purity, of
  knowledge, and of emancipation. This is the fourth quality of the
  ocean inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those five qualities of food which you said were inherent in Nirvâna,--which are they?'
  
  
  'As food, O king, is the support of the life of all beings, so is
  Nirvâna, when it has been realised, the support of life, for it
  puts an end to old age and death. This is the first quality of food
  inherent in Nirvâna. And again, O king, as food increases the strength
  of all beings, so does Nirvâna, when it has been realised, increase
  the power of Iddhi of all beings. This is the second quality of food
  inherent in Nirvâna. And again, O king, as food is the source of the
  beauty of all beings, so is Nirvâna, when it has been realised, the
  source to all beings of the beauty of holiness. This is the third
  quality of food inherent in Nirvâna. And again, O king, as food puts
  a stop to suffering in all beings, so does Nirvâna, when it has been
  realised, put a stop in all beings to the suffering arising from every
  evil disposition. This is the fourth quality of food inherent in
  Nirvâna. And again, O king, as food overcomes in all beings the
  weakness of hunger, so does Nirvâna, when it has been realised,
  overcome in all beings the weakness which arises from hunger and every sort of pain. This is the fifth quality of food inherent in
  Nirvâna.'
  
  
  'Venerable Nâgasena, those ten qualities of space which you said were inherent in Nirvâna,--which are they?'
  
  
  'As space, O king, neither is born nor grows old, neither dies nor
  passes away nor is reborn, as it is incompressible, cannot be
  carried off by thieves, rests on nothing, is the sphere in which birds
  fly, is unobstructed, and is infinite; so, O king, Nirvâna is not
  born, neither does it grow old, it dies not, it passes not away, it
  has no rebirth, it is unconquerable, thieves carry it not off, it
  is not attached to anything , it is the sphere in which Arahats
  move, nothing can obstruct it, and it is infinite. These are the ten
  qualities of space inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those three qualities of the wish-conferring gem which you said were inherent in Nirvâna,--which are they?'
  
  
  'As the wishing-gem, O king, satisfies every desire, so also does
  Nirvâna. This is the first quality of the wishing-gem inherent in
  Nirvâna. And again, O king, as the wishing-gem causes delight, so
  also does Nirvâna. This is the second quality of the wishing-gem
  inherent in Nirvâna. And again, O king, as the wishing-gem is full
  of lustre, so also is Nirvâna. This is the third quality of the
  wishing-gem inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those three qualities of red sandal wood which you said were inherent in Nirvâna,--which are they?' 'As red
  sandal wood, O king, is hard to get, so is Nirvâna hard to attain to.
  This is the first quality of red sandal wood inherent in Nirvâna. And
  again, O king, as red sandal wood is unequalled in the beauty of its
  perfume, so is Nirvâna. This is the second quality of red sandal wood
  inherent in Nirvâna. And again, O king, as red sandal wood is praised
  by all the good, so is Nirvâna praised by all the Noble Ones. This is
  the third quality of red sandal wood inherent in Nirvâna.'
  [322] 'Venerable Nâgasena, those three qualities of the skimmings of ghee 1 which you said were inherent in Nirvâna,--which are they?'
  
  
  'As ghee is beautiful in colour, O king, so also is Nirvâna
  beautiful in righteousness. This is the first quality of the ghee inherent in Nirvâna. And again, O king, as ghee has a pleasant
  perfume, so also has Nirvâna the pleasant perfume of righteousness.
  This is the second quality of ghee inherent in Nirvâna. And again, O
  king, as ghee has a pleasant taste, so also has Nirvâna. This is
  the third quality of ghee inherent in Nirvâna.'
  
  
  'Venerable Nâgasena, those five qualities of a mountain peak which you said were inherent in Nirvâna,--which are they?'
  
  
  'As a mountain peak is very lofty, so also is Nirvâna very
  exalted. This is the first quality of a mountain peak inherent in
  Nirvâna. And again, O king, as a mountain peak is immoveable, so
  also is Nirvâna. This is the second quality of a mountain peak
  inherent in Nirvâna. And again, O king, as a mountain peak is
  inaccessible, so also is Nirvâna inaccessible to all evil
  dispositions. This is the third quality of a mountain peak inherent
  in Nirvâna. And again, O king, as a mountain peak is a place where no
  plants can grow, so also is Nirvâna a condition in which no evil
  dispositions can grow. This is the fourth quality of a mountain peak
  inherent in Nirvâna. And again, O king, as a mountain peak is free
  alike from desire to please and from resentment, so also is Nirvâna.
  This is the fifth quality of a mountain peak inherent in Nirvâna.'
  
  'Very good, Nâgasena! That is so, and I accept it as you say.'


If you are a beginner student to Buddhism, what is important to understand is the words 'birth' &amp; 'death' mean conceiving the thoughts: "I am born" &amp; "I will die", as described in MN 140. Therefore, in Nibbana, there is no birth &amp; no death because there is no view of "I am" or "self". 


  The tides of conceiving do not sweep over one who stands upon these
  foundations, and when the tides of conceiving no longer sweep over him
  he is called a sage at peace.’ So it was said. And with reference to
  what was this said?
  
  “Bhikkhu, ‘I am’ is a conceiving; ‘I am this’ is a conceiving; ‘I
  shall be’ is a conceiving; ‘I shall not be’ is a conceiving; ‘I shall
  be possessed of form’ is a conceiving; ‘I shall be formless’ is a
  conceiving; ‘I shall be percipient’ is a conceiving; ‘I shall be
  non-percipient’ is a conceiving; ‘I shall be
  neither-percipient-nor-non-percipient’ is a conceiving. Conceiving is
  a disease, conceiving is a tumour, conceiving is a dart. By overcoming
  all conceivings, bhikkhu, one is called a sage at peace. And the sage
  at peace is not born, does not age, does not die; he is not shaken and
  does not yearn. For there is nothing present in him by which he might
  be born. Not being born, how could he age? Not ageing, how could he
  die? Not dying, how could he be shaken? Not being shaken, why should
  he yearn?
  
  MN 140