post of Potions master (HBP8)
The tiny little Charms master was bobbing his way toward them... (HBP24)
Charms master (DH30)
A teacher; a person qualified to teach (NSOED). This is often used in compound form with the name of the subject the person teaches. For a woman, “mistress” would be used in the same way, e.g., “Headmistress”.