1) A large female posterior, combined with a slim waist
2) A woman possessing the above.
3) A nickname for a specific girl possessing the above.
1) "I wank to cream in her badunkadunk."
2) "She used to be slim, but The Pill turned her into a badunkadunk."
3) "Her? Yeah, that's Badunkadunk. Careful, she bites."