1) to gladden, make joyful
1a) to be glad, to be merry, to rejoice
1b) to rejoice in, be delighted with a thing
Part of Speech: verb
Citing in TDNT: 2:772, 278
From G2095 and G5424; to put (middle voice or passive voice be) in a good frame of mind, that is, rejoice: - fare, make glad, be (make) merry, rejoice.
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 εὐφραίνω; click on the second column to search for that grammatical form of the root εὐφραίνω; click on the third column to search for that word and grammatical form; click on the total to search for the root εὐφραίνω.