Wiktionary
knee-trembler
n. (context slang English) a casual outdoor sexual encounter (commonly with a prostitute), usually in an alleyway or against a wall, with the man standing and the woman's knees raised
Usage examples of "knee-trembler".
Back to her brownstone, an explanatory chat with her mum, a silent, grateful handclasp from her dad, a game of checkers with her little brother, and, as I took my leave, a royal knee-trembler in the rumpus-room.
And if I hadn't any money, I'd just have to give him a four-penny knee-trembler, for free.
And if I hadn’t any money, I’d just have to give him a four-penny knee-trembler, for free.
The alley itself used by ladies of the night for knee-tremblers and God knows what else.