Masturbation. Basically, if no one else is around, who are you going to beat it to but the mattress?
"John was beating the mattress so hard last night that I heard it through the wall."
"Jessica's out tonight. Guess it's me and the mattress."
"Jessica's out tonight. Guess it's me and the mattress."
by Apple-sucker July 26, 2012
Get the Beating the Mattressmug.