I. ˈwau̇ interjection
Date: 1513
— used to express strong feeling (as pleasure or surprise)
II. noun
Date: 1920
: a striking success : hit
III. transitive verb
Date: 1924
: to excite to enthusiastic admiration or approval
a performance that wow ed the critics
IV. noun
Etymology: imitative
Date: 1932
: a distortion in reproduced sound consisting of a slow rise and fall of pitch caused by speed variation in the reproducing system