1) a money changer, money broker
Part of Speech: noun masculine
From a derivative of G2772; a handler of coins, that is, money broker: - changer of money.
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 κερματιστής; click on the second column to search for that grammatical form of the root κερματιστής; click on the third column to search for that word and grammatical form; click on the total to search for the root κερματιστής.