Bigass

a combining form of -ss in the sense of ‘stupid person’ or ‘the b-ttocks’, used in slang words as an intensifier or with disparaging intent: big–ss; stupid–ss.
adj.

pretentiously large: abraham opened the door of his big-ss cadillac
pretentious; self-important: his goddam big–ss face

used to form adjectives
having b-ttocks of the specified sort: big–ss/ fat-ssed
used to form adjectives and nouns 2 having a specified character or nature to a high degree: bad-ss/ wild-ssed/ silly–ss