a larger-than-average rounded booty. "Thick" is pretty self-explanatory. To be considered "juicy," it must shake like jelly when slapped, must be well-rounded (no flat or square asses), and the woman must have a reasonably good waist/hips ratio.
Known to appeal strongly to black and hispanic men, though as the song goes, sometimes "even white boys got to shout."
i love to hit Diane doggy-style so I can watch her grind that thick-n-juicy into my cock.