A non-cliche variant on the common jack-off or jagoff. Also a substitute for 'douchebag'
So he made life miserable for everyone here, then whined through the entire process of being fired, then said he hated his job and was already looking for another one anyway. What a jackloaf...
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.