English▸ noun a person who dishonestly claims to have special knowledge and skill in some field, typically medicine:
[as modifier] a quack doctor
quack cures.
▪ British English informal a doctor:
he went to see the quack this morning.
– ORIGIN mid 17th century: abbreviation of earlier quacksalver, from Dutch, probably from obsolete quacken ‘prattle’ + salf, zalf (see salve1).