boomerang boob
A boob so loose that when moving it jiggles around and hits/slaps you in the face.
'did you see that girl in the gym running on the treadmill?'
'yea she looks as though she was about to get knocked out'
'yeaa she got that boomerang boob!'
'yea she looks as though she was about to get knocked out'
'yeaa she got that boomerang boob!'