Is it possible to describe nibbana? This Dhamma Wiki article, Nibbana, says that "Nibbana (Pali), nirvana (Sanskrit), is the highest spiritual state and the ultimate goal of Buddhism."

Please describe nibbana. What is it? How do you know you are in Nibbana?

How can somebody describe Nibbana if it's impossible to know what follows after death?
It is possible to describe the nibbana, but non ariya practitioner can't understand the description.

In abhidhamma taught that the non ariya practitioner can't know the real nibbana, until he will be ariya. Because he has not enough ability.