knock boots (with one)
euphemism To have sex (with one). My roommate in college used to hang a hat on the door handle outside our room if she was knocking boots with someone inside. I could tell he was more interested in knocking boots than in having any kind of serious relationship.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
tv. to copulate. He said he wanted to knock boots with her.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.