Put down a three (3)

to masturbate.

the third type of male body excretion.

to go number one is to pee. number 2 is to poop. so number three is to release semen from a dude's body.

a person can't "go number three" because, unlike a deuce, it can't just be pushed out of the body. Hence it has to be "put down".
"I was going to return your call, but I was busy putting down a three."

"This video game is so awesome, it makes me want to put down a three."

"That guy Rick is such a loser, I bet he puts down a lot of threes,"
by JiffMart May 2, 2010
Get the put down a three mug.