When a gay couple is having sex and the pitcher punches the receiver in the asshole as hard as possible and then thrusts his penis into said asshole before the receiver can get away.
Someone or something that bites your ankles.
To a postman, an ankle biter is often known as a dog.
To an adult, an ankle biter may be a toddler.
To hikers, an ankle biter is sometimes a tick.
And so on.