QUACK, verb intransitive 1. To cry like a duck or goose. 2. To boast; to bounce; to talk noisily and ostentatiously; as, pretenders to medical skill quack of their cures. QUACK, noun [from the verb.] 1. A boaster; one who pretends to skill or knowledge which he does not possess. 2. A boastful pretender to medical skill which he does not possess; an empiric; an ignorant practitioner.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI