1) to pluck off, pull out
2) to cause to vibrate by touching, to twang
2a) to touch or strike the chord, to twang the strings of a musical instrument so that they gently vibrate
2b) to play on a stringed instrument, to play, the harp, etc.
2c) to sing to the music of the harp
2d) in the NT to sing a hymn, to celebrate the praises of God in song
Part of Speech: verb
Citing in TDNT: 8:489, 1225
Probably strengthened from ψάω psaô (to rub or touch the surface; compare G5597); to twitch or twang, that is, to play on a stringed instrument (celebrate the divine worship with music and accompanying odes): - make melody, sing (psalms).
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 ψάλλω; click on the second column to search for that grammatical form of the root ψάλλω; click on the third column to search for that word and grammatical form; click on the total to search for the root ψάλλω.