This is normally associated with sexual intercourse carried out at a rough and vigorous pace (most commonly doggy-style), although it can be associated with any activity where it is performed with gusto. This means that you did whatever it was you were doing with particular enthusiasm and/or speed
Good morning Casper. I had a cracking time knocking the back out of Lady Clementine Smyth last night
or
Gadzooks, I could certainly knock the back out of a few glasses of Moet this evening
Marlowe woke up on the floor with a hangover and throbbing from a blow to the head. He poured half a tumbler of bourbon and knocked it back. Not a cure but would have to do for first aid.
(past tense of "knock it back")
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!
Sister: This meeting was to discuss the rough draft of my essay, where we discussed the subsidiary questions I added in my rough draft. We also discussed the relationship between my main title and the real-life situations I chose to use in my essay. We discussed the structure of my essay as well, specifically the Math AOK section and how it relates to the contradiction of the title. This second meeting was particularly helpful in discussing the implications of my essay claims and how to apply the title across various areas of knowledge. There were many sections of the essay that could have been cut down in wordiness and the ways of knowing required further and more in-depth analysis.
An absolutely foolproof way to keep minors from viewing content deemed "too mature" for them to watch.
Billy: "So I was trying to watch some videos for an M rated game, and I ran into an age gate, so I put in my real birthday. SOMEHOW it managed to figure out that I am 12. CURSE YOU AGE GATE!!!"
Bill: "Fucking age gate! *quick scroll* THERE! I was born on January 1, 1904. Fuck you age gate."