A B cube refers to a rotund woman who must possess 3 essential qualities - big boobs, a big butt and a big belly. Since these 3 qualities all start with the letter 'B', she is therefore known as a B cube or a B cuber.
Jesus, Dan sure attracts those B cubers at the club!
Did you see the B cube Dan got with last night? She was oozing oil on the dancefloor!
Man, I wish my girlfriend was a B cube, just like Dan's!