The maneuver wherein, while preparing
to engage in sexual behavior, the male partner of the couple suddenly turns his partner around and proceeds to penetrate him/her anally. Usually used
with "the ol'" in front
of it, as below.
This is derived from the name of the character in the film "Brokeback Mountain" on whom
this maneuver was performed.
her think he was after
some oral, but he gave her the ol' jack
"Ennis wasn't about to blow him, so he gave that cowpoke the ol' jack