Webster's Revised Unabridged Dictionary · 1913

Whew

Whew (hwū) , noun and interjection

A sound like a half-formed whistle, expressing astonishment, scorn, or dislike.
Collocations (1)
Whew duck , the European widgeon. [Provincial English]

Whew , intransitive verb

To whistle with a shrill pipe, like a plover. [Provincial English & Scottish]