simply a baby that pops out of your anus without warning
person 1: holy crap! that baby just came out of my ass hole!!!
person 2: it's called an anus baby.
A person so incredibly annoying, that the only was to describe him is that they were pushed out of their mother's anus.
Fool, your such an anus baby, you cant just jizz off the porch.
You fucking anus baby dont touch me.