When you kneel over your ol' lady while she lays flat on her back throating your pecker and you drop your "coal" (bowel movement) on her chest proceeding to yell Choo choo.
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."