It's when you are skinny dipping with some ladies in Lake Michigan and follow up by doing one of them in the ass. Then later that night you go and do the same thing with some of your closet gay friends.
This is a maneuver that requires both a male and female, excluding guy on guy since it will require an unobstructed anus. this however does not exclude girl on girl if a strap-on is readily available. This act starts off with the man(or the man in the relationship) sitting on the toilet facing the tank, and then the reciever mounting the the male. after starting intrecourse the female then procedes to shit which on most occasions will leave a trail of fecal matter on the scrotum.
"man i cant believe that girl did a michigan moose track double stack with me last night, and she wasn't even that drunk either!"
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
"Base we've got some square groupers floating outside of Miami harbor."