A visual description of the labia minora resembling a thinly sliced piece of rare roast beef hanging like a drape. This resemblance is more pronounce on women whose labia minora overhangs her labia majora leaving the edges darker in tone to the pink or ruby color of the inner vagina. Most commonly used when referring to cunnilingus or "going down" on your girl, a particularly pleasurable form of foreplay.
"Hey baby, you mind if I taste me some of your roast beef curtain?"
"I'm takin' her home for some roast beef curtain. Know wha'I'm sayin'?"
"Maybe I could have a bit of your roast beef curtain while I wait for Mr. Viagra?"