The wrongful act of an officer or other person in compelling payment of a fee or reward for his services, under color of his official authority, where no payment is due.
Between “extortion” and “exaction” there is this difference: that in the former case the officer extorts more than his due, when something is due to him; in the latter, he exacts what is not his due, when there is nothing due to him. Co. Litt 368.