Definition: a morally unprincipled person
“Reprove” means to scold or express disapproval of someone. A “reprobate” is technically someone on the receiving end of that disapproval.
Why I Looked It Up
On the back of a romance novel:
When Elizabeth laid eyes on drunk, disorderly Sam, the disdain was more than mutual. The crude, uncivilized reprobate was her escort? Why, she’d be safer in a bed of rattlesnakes!