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.
"He made her think he was after some oral, but he gave her the ol' jack twist!"
"Ennis wasn't about to blow him, so he gave that cowpoke the ol' jack twist."