A sexual position involving two guys and a girl. The girl gets on all fours, and the two guys face each other, one with his dick in her ass and the other with his dick in her mouth. The lumberjack is a coordinated, synchronized motion by the two guys whereby when one is thrusting his cock in on one end, the other is pulling his cock out at the other end. They do this back and forth and this synchronized thrusting creates the illusion of two lumberjacks using an old-time hacksaw (the long ones with handles at both ends) to saw through a tree trunk.
Joe and Bob picked up a hooker and gave her the Lumberjack.