piss sonar

The echolocation tool men use when they piss in the dark to make sure they're hitting the toilet. This involves starting to urinate and listening carefully for the sound of the urine stream hitting the toilet water. If the sound is not heard, aiming adjustments are made until such time as the reassuring sound is heard.

Joe: "Man, I got home last night drunk, went in the bathroom, didn't turn on the light and ended up pissing all over the bathroom floor."
Bob: "You should have used piss sonar to find the toilet, bro."
Joe: "Oh."