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Webster 1913 Edition

Noun.

One who, or that which, stuns.

Something striking or amazing in quality; something of extraordinary excellence.

[Slang]

Thackeray.

stunner ‎(plural stunners)

(colloquial) Anything that is stunning.
(colloquial; variant spelling stunna) Specifically, a woman of stunning beauty (often hyperbolically).

anything that is stunning

woman of stunning beauty