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When two women lay down, one on top on the other (missionary style). They then push their vaginas together and the male(or for lack of male, third woman with a strap-on) comes in and fucks the spot in between them. This stimulates the clits of both women and the male's penis at the same time and everyone has a great time.
Guy 1: So I heard you banged Susan and Candy at the same time last night, you pimp!

Guy 2: Yeah, I got them both drunk and had myself a clam sandwich.
by DeadEyeD!ck February 08, 2009
Two vaginas are pressed togther with a thin layer of roast beef placed in bewteen! It is a thinly sliced lean roast beef pressed between two hairless clams.
Excuse me... is that a clam sandwich that you two lovely ladies are displaying? Yes, we are pushing our pussies togther and, yes, this is roast beef inbetween!
by Dr. Felchenstien May 20, 2004