As a noun quack
is the sound made by a duck or
quack can be a fraudulent healer or incompetent professional, especially a doctor of medicine; an impostor who claims to have qualifications to practice medicine.
As a verb quack
is to make a noise like a duck or
quack can be to practice or commit quackery.
As an adjective quack
is falsely presented as having medicinal powers.
As a proper noun crow is
a native american tribe or
crow can be .