A bad lie that only works because it is socially awkward or embarrassing. Used to quickly end an interrogation.
At college, a guy walks in on his roommate, who was using a computer. The roommate quickly quits off the program.
Guy: What were you just doing?
Roommate: Watching porn.
Guy: Oh *walks away*
Roommate was actually playing World of Warcraft. Porn was a wet lie.
Parents hear something aggressive from son's bedroom and go over to check it out. They knock loudly on the door. Son answers, naked and a little sweaty, barely creaking the door open.
Dad: What's going on in there?
Son: Nothing... I was just masturbating...
Mom: Why are you so sweaty?
Son: I was really getting into it
Parents: *walk away*
What really happened was the boy was having sex with some girl. Masturbation was a wet lie