To do something horribly, horribly stupid that leaves you wide open to be screwed, like in a prison shower. Screwage may be figurative or literal.
"I dropped the soap! Now I'm as good as screwed!"
To "Drop the soap" is to accidently, or absent mindedly, put yourself in a vulnerable position. Derived from the idea that in a prison shower, if you were to drop the soap, and bend over to pick it up, you would expose your anus to rape.
"We're surrounded, don't make any sudden moves, and for christ's sake don't drop the soap!"
A situation in which leaves you in a suggestible position for painful, embarrasing and/or discouraging consequences
The prison guard's words "Don't drop the soap" was the only time he had before the inmates raped him
Crap!, I dropped the soap and my house got repo-ed. I'm totally f---ed now!
To have anal intercourse, derived from the term "don't drop the soap"
Guy: Hey, you wanna drop the soap?
Girl: Oh yeah, lets get it on