1) a touchstone, which is a black siliceous stone used to test the purity of gold or silver by the colour of the streak produced on it by rubbing it with either metal
2) the rack or instrument of torture by which one is forced to divulge the truth
3) torture, torment, acute pains
3a) of the pains of a disease
3b) of those in hell after death
Part of Speech: noun masculine
Citing in TDNT: 1:561, 96
Perhaps remotely from the same as G939 (through the notion of going to the bottom); a touch stone, that is, (by analogy) torture: - torment.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root βάσανος; click on the second column to search for that grammatical form of the root βάσανος; click on the third column to search for that word and grammatical form; click on the total to search for the root βάσανος.