I. ˈnäk-ˌau̇t noun
Date: 1887
1.
a. : the act of knocking out : the condition of being knocked out
b.
(1) : the termination of a boxing match when one boxer has been knocked down and is unable to rise and resume boxing within a specified time
(2) : technical knockout
c. : a blow that knocks out an opponent
2. : a sensationally striking, appealing, or attractive person or thing
II. adjective
Date: 1818
1. : causing a knockout
a knockout blow
2. : sensationally striking, appealing, or attractive
a knockout dress
3. : having all or part of a gene eliminated or inactivated by genetic engineering
knockout mice predisposed to diabetes mellitus