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

When someone goes to the gym and spends 90% of the time on their phones scrolling through social media

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

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

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.

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

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.