I recommend the Digital Pali Reader (a browser extension for Firefox and Pale Moon ).
buddhism.stackexchange.com/users/7031/labaleine
Wisdom Library is one of the most reliable.
E.g. Samma Samadhi .
Also Access To Insight has a glossary.
buddhism.stackexchange.com/users/295/Suminda Sirinath S. Dharmasena
For Sanskrit I use http://spokensanskrit.de/ and for Pali http://dsal.uchicago.edu/dictionaries/pali/
buddhism.stackexchange.com/users/43/Andrei Volkov
I've tried the PTS Pali-English dictionary (for Pali).
There's a trick to using it though.
Enable Search entry words only (not definitions)
Type in the word you're looking for e.g. Samadhi When you search
it may not find the result.
So: Also select Words starting with (Example: bud) Type in fewer (just the first few) letters of the word you're looking for e.g. Sama
This may display several results --
hopefully you can find the word you're looking for on this list (maybe Samatha in this case).
This searching for a prefix (instead of for the full word) if often necessary, because Pali words have declensions and conjugations when they're used in sentences, which alters their suffixes.
I think that samadhi versus samatha (used in the example above) is a difference between Sanskrit and Pali.
The fact remains, however, that when looking for Pali words in the PTS dictionary
it's often necessary to search for the prefix.
Another reason why that's so is, I think, that Pali words are joined together (like in German).
Look at this answer for example (which uses the Critical Pali Dictionary instead of the PTS dictionary), which shows for example various words created from ārāma .
I note that ārāma isn't in the PTS dictionary however arañña is — which is another reason why you may need to look for prefixes (I found it by searching the PTS dictionary for ara after a search for aram found no results), i.e. that the Latinesque alphabet spelling might not be standardized.
Beware that the PTS dictionary requires of you a semi-exact spelling when you do a lookup, for example to find Kālika
you must search for Kālika (and searching for Kalika won't find it).
There's also this Glossology .
It only lists dhamma-related words (so it's not a full dictionary), but its entries are a bit fuller than the dictionaries'.
buddhism.stackexchange.com/users/254/ChrisW
Princeton Dictionary of Buddhism is another source.
http://www.international.ucla.edu/institute/article/149341
buddhism.stackexchange.com/users/5437/ramana_k
I found this one, which seems to aggregate answers from several different dictionaries.
Still a LOT of words missing from the Dhammapada (which I'm working on adapting) but a very useful resource for trying to pick apart Pali texts: http://dictionary.sutta.org/
buddhism.stackexchange.com/users/12803/jerclarke
For Pali , I use The Pali Text Society's Pali-English dictionary .
Here are the options I choose for best results (in general) i.e. Search entry words only and Words starting with (as mentioned by ChrisW in his answer) For Sanskrit , I use Sanskrit Dictionary and Spoken Sanskrit .
I will even use Wiktionary e.g. for etymological information.
In fact, I tend to look up a Pali word, explore its Sanskrit ancestor/relative in the Sanskrit Dictionary and then check etymology in Wiktionary.
buddhism.stackexchange.com/users/10802/Simon H
I believe that there many words translate from Buddha Sutra and I want to ask is there any website can translate the words meaning in English? Example Samman Samadhi
Are there any websites that contain Buddhist dictionaries?
buddhism.stackexchange.com
<terminology>
buddhism.stackexchange.com/questions/11877
buddhism.stackexchange.com/users/7036/Le Parkour
Numerous Pali online references exist including  http://www.international.ucla.edu/institute/article/149341, PTS Pali-English dictionary  (for Pali), Wisdom Library and http://spokensanskrit.de/  and for Pali  http://dsal.uchicago.edu/dictionaries/pali/. Suggested websites and resources include the following: the Digital Pali Reader  (a browser extension for Firefox and  Pale Moon); PTS Pali-English dictionary; Princeton Dictionary of Buddhism; http://www.international.ucla.edu/institute/article/149341; Wisdom Library; http://dictionary.sutta.org/; The Pali Text Society's Pali-English dictionary;  the Access To Insight glossary;  http://spokensanskrit.de/ for Sanskrit and  http://dsal.uchicago.edu/dictionaries/pali/ for Pali.
Suggested websites and resources include the following: the Digital Pali Reader  (a browser extension for Firefox and  Pale Moon); PTS Pali-English dictionary; Princeton Dictionary of Buddhism; http://www.international.ucla.edu/institute/article/149341; Wisdom Library; http://dictionary.sutta.org/; The Pali Text Society's Pali-English dictionary;  the Access To Insight glossary;  http://spokensanskrit.de/ for Sanskrit and  http://dsal.uchicago.edu/dictionaries/pali/ for Pali.