1) an assassin
1a) one who carries a dagger or short sword under his clothing, that he may kill secretly and treacherously any one he wishes to
1b) a cutthroat
Part of Speech: noun masculine
Citing in TDNT: 7:278, 1026
Of Latin origin; a dagger man or assassin; a freebooter (Jewish fanatic outlawed by the Romans): - murderer. Compare G5406.
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 σικάριος; click on the second column to search for that grammatical form of the root σικάριος; click on the third column to search for that word and grammatical form; click on the total to search for the root σικάριος.