The act of engaging, after a solid regimen of vaginal sex, in the act of anal sex; also known as sodomy. One can also hop onto the back nine right away if possible. This phrase is a simile derived from the game of golf when one plays the last nine holes on an 18 hole golf course.
Me and my girlfriend were having great sex last night when all of a sudden we tried to switch it up and ended up "playing the back nine" wink* wink*.
by TigersWood April 05, 2011