1) a Hellenist
1a) one who imitates the manners and customs or the worship of the Greeks, and use the Greek tongue
1b) used in the NT of Jews born in foreign lands and speaking Greek
Part of Speech: noun masculine
Citing in TDNT: 2:504, 227
From a derivative of G1672; a Hellenist or Greek speaking Jew: - Grecian.
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 Ἑλληνιστής; click on the second column to search for that grammatical form of the root Ἑλληνιστής; click on the third column to search for that word and grammatical form; click on the total to search for the root Ἑλληνιστής.