Crossword Genius

(Slang) unfamiliar vocabulary (5)

Ross

I believe the answer is:

lingo

(Other definitions for lingo that I've seen before include "Specialised vocabulary" , "Jargon, foreign language (informal)" , "Language, colloquially speaking." , "Vernacular" , "Log in (anag.)" .)

I've seen this clue in The Guardian.
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