A creative way of speaking about sexual parts
Eg. "His dimensions were seriously disappointing" or, "She had good dimensions up top, not a bad package all up."
To say that someone has dimensions is another way to say that someone is an arsehole. Stemmed from the colloquial phrase noting that someone's 'interesting'...
"What do you think of my new Jamaican girlfriend mum?"
"She has dimensions... *bitch!*"