The act of performing anal sex but preventing from having vaginal sex to remain a “virgin”. Usually people do this for religious reasons.

The clause by which a female may circumvent the moral law which dictates that a female should not engage in sexual relations prior to marriage by participating in anal sexual relations in lieu of vaginal intercourse. Additionally, the female will conveniently avoid risk of pregnancy while simultaneously preserving her virginity.

The logic that allows girls who are saving their virginity for marriage to instead have premarital anal intercourse.
Typically the boyfriends of such girls will convince them that, if they take it in the ass and don't pop the cherry, they're still pure and virginal.

When a girl desperately wants to keep her virginity but needs some good back-door romance

A sexual activity engaged in when conservative girls want to remain virgins so they only have anal coitus.

Taking it in the ass in order to preserve your virginity.

When children use the need to go to the bathroom and make a deuce as an irrefutable excuse to get out of bed at night.