Definition of Quackish

Babylon English Dictionary
impersonating, posing; involved in deceit
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Quackish Definition from Language, Idioms & Slang Dictionaries & Glossaries
Webster's Revised Unabridged Dictionary (1913)
(a.)
Like a quack; boasting; characterized by quackery.
  
Webster's Revised Unabridged Dictionary (1913), edited by Noah Porter. About
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quackish
\quack"ish\, a. like a quack; boasting; characterized by quackery.