butt bunny
a small mound of skin or 'nubbit' that emerges within the soft wrinkles of one's lover's butthole, often as a result of repeated anal sex. Although technically an anal fissure, it is usually not due to complete negligence of lubrication or aggressiveness in a single act, but rather because of the lovers' shared undying lust and eagerness to engage in this highly intimate act, developing over many sessions. Therefore, while often initially a cause of concern, it can often be seen with endearment, a sign of each other's sexual history and commitment, and a reminder for the necessity for ample care, tenderness and lubrication when ass play begins. It can also be regarded by kinksters in committed relationships as a symbol of their initiation into the world of BDSM, and even usually signifies an ability to take it without as much resistance. sometimes the area's sensitivity can even be stimulated by the tongue to cause more pleasure in this erogenous zone, and be seen as an anal or vag-anal clitoris.

it can also be a clear sign to a boyfriend that the relationship has reached a level of sexual intimacy makes his judgement of superficial 'flaws' unwarranted. He may realize at this point that though he may fancy himself a true cocksmith, he is just a greasy little perv with a crooked dirty dick.
example:

GF: "I'm a little self conscious about my asshole. i think i got a little nubbit down there."
(boyfriend inspects)
BF: "aw hunny, its no big deal, i've seen tons of porn stars with one of those. its actually.. kind of cute. does it hurt?"
GF: "No, it kind of feels good. just stretched out. I guess it will just be my little Butt Bunny."
BF: "I'm pretty sure i got a couple swollen wrinkles myself after you pegged me last week. they can be OUR Butt-Bunnies, hunny bunny"