A red mushroom is when a male cant get hard so he slaps his woman across the face with his jimmer-jammer untill it gets hard leaving a red mark resembling a mushroom.
"Dude, I couldn't get hard so i gave Angelina a red mushroom last night."
"Who?"
"Angelina, you know, the slut bomb."
"Who?"
"Angelina, you know, the slut bomb."
by ETK&EWTD January 23, 2006