A corsican dialect refers to a blowjob. It can be split to two words. The word "dialect" is commonly used as a synonym to "conversation", in this given cause, meaning oral pleasuring of a penis. The word "corsican" refers to a southern island in the mediterranean sea that is considered a region of france. It's connection to a blowjob is yet unknown.
Hey, did you know where Jim and Mary went?
They are having a Corsican dialect in the bathroom.
A corsican dialect is a commonly used discrete reference for a blowjob. An excelent way of avoiding the use of more offensive words in public.
Person 1 -"Hey, do you know where Jake and Kate went?"
Person 2 -"Uh, they're having a corsican dialect."
Person 1 -"Wow.. at a grill party?"
Person 2 -"Yeah, so don't spread it"