I'd Knock The Back Out Of That! Edit Meaning

1.

Said about a sexually appealing woman, with whom you would be very eager to have sex.

To explain the metaphor: you may be a little too vigorous, and push your penis all the way through her, hence, knocking the back out of her... Obviously not physically possible, but a good, although rather crude, metaphor

Guy A: Phwoar, Check her out, what a stunner!

Guy B: God yeah, I'd knock the back out of that!

See fuckable, i'd tap that, i'd break her pelvis, hott