/ kwæk; NAmE / noun , verb
■ noun
1.
the sound that a duck makes
2.
( informal , disapproving ) a person who dishonestly claims to have medical knowledge or skills :
quack doctors
I've got a check-up with the quack (= the doctor) next week.
■ verb
[ v ] when a duck quacks it makes the noise that is typical of ducks
••
WORD ORIGIN
noun sense 1 and verb mid 16th cent. (as a verb): imitative.
noun sense 2 mid 17th cent.: abbreviation of earlier quacksalver , from Dutch , probably from obsolete quacken prattle + salf , zalf (see salve ).