Lingo or jargon (5)
I believe the answer is:
argot
I believe this is a double definition.
'lingo' is the first definition.
(synonyms)
'jargon' is the second definition.
(synonyms)
(Other definitions for argot that I've seen before include "Talk of thieves" , "Particular group's jargon" , "Slang, patois" , "Slang for a groat (5)" , "manner of speaking" .)