An extreme variation of roast beef or meat curtains; a horsemeat sandwich is often characterized by distinctive public hair. Excessive length of the labia renders shaving the area difficult or downright impossible. The horsemeat appearance stems from an anomalous protrusion of the inner lips from the labia majora. It's gross.
I heard Katey's rockin' a horsemeat sandwich; whatever you do, don't go down on her.
by Bill Sampson, Esq. April 23, 2008