n. （鸭子）嘎嘎叫声
v. （鸭子）嘎嘎叫；大声闲聊（quack的ing形式）

Quack \Quack\, v. i. [imp. & p. p. {Qvacked}; p. pr. & vb. n.
{Quacking}.] [Of imitative origin; cf. D. kwaken, G. quacken,
quaken, Icel. kvaka to twitter.]
1. To utter a sound like the cry of a duck.

2. To make vain and loud pretensions; to boast. `` To quack
of universal cures.'' --Hudibras.

3. To act the part of a quack, or pretender.