It's when a girl (or a guy) is riding you with her front facing you and you start poopin in your hands secretly. Then you take the poop and you rub it up and down the girl's back like a washboard.
John drew a smiley face after giving Jeff a Wooster Washboard.
by Kirk Johnson September 06, 2006
Actually, it is not necessary to "snot rocket" down the washboardee's throat, but rather they may clean out the washboarder's nostrils with their tongue. This alternate strategy is also deemed a washboard.
Dude, I can totally breathe better now that Erika gave me that Wooster Washboard.
by DeQwan Jackson September 07, 2006