The coded, obscure, and impenetrable language used among experts in a particular field, impossible to be understood by people not trained in that field.
"I didn't get a thing out of attending that seminar. The lectures were all in expertese."
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.