This is a term that describes someone who thinks they wet the bed, when in fact they did not. This typically happens when a couple who are completely obliterated have sex. The male has most likely been holding in piss like his bladder was the Hoover Dam and right at the climax, he has no control of the floods and fills his partner with semen and urine. He then rolls over and is out cold in seconds. The female, who is also drunk, has no idea he went number 1 inside her and also rolls over to go to sleep. She wakes up hours later in a puddle of piss that was not hers.
Big Easy: Dude, last night was a train wreck. My wife keeps apologizing to me for wetting the bed but she really didn't.

Tyrant: Not following you there bud.

Big Easy: I think I pissed insider her last night and didn't want to tell her.

Tyrant. Well you can't ever tell her about the third party bed wetting.
by Uncle Gary's Potato Farm February 22, 2019
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