A person that has suffered several mutations, gifting them with several resistances and magical powers. These folk are tasked with the hunting of monsters, dispelling of curses and concocting of potions, for a fair price.
I had to hire a witcher to help me with a curse that was haunting my daughter. - some peasant.
A person that underwent rigorous training, suffered several mutations and has been gifted with several resistances and magical powers. They're tasked with the killing of monsters, dispelling of curses and concocting of potions, in exchange for coin.
Peasant: I hired a passerby Witcher to kill the drowners by the bridge. He should be done by now.