When you wife/girlfriend is not in the mood and she rolls over facing away from you, where her ass is next to you. Generallythishappens just before she falls asleep, when thishappens your wife/girlfriend is generally not in to anal play.
husband: wanna play around?
wife:sure after this show, (wife turns on side away from you)
husband: well you are giving me the ass so i guess i will see ya in the morning!