"Your buttocks is big."
Translation:Tha do thòn mòr.
Agree with those saying that in English English buttocks is a plural noun and should be "your buttocks are big". (Can't speak for American English.) But I don't think anyone in England would say this is a sentence anyway these days unless a farmer was talking about the buttocks on an animal. For a person I think you would be saying your bottom or bum or ar*e or rear.