Knockout vs. Knock Out
“Knockout” is a closed noun for a boxing result, elimination format, or striking person or thing, and it can also be an adjective. “Knock out” is the phrasal verb for making someone unconscious, eliminating a competitor, disabling equipment, or producing something quickly.
Use “knockout” as the noun or adjective; use “knock out” as the phrasal verb.
Key details
Choose the right form
| If you mean / need | Use | Why |
|---|---|---|
| a result, competition format, or describing adjective | knockout | It is the noun/adjective form. |
| the action of making unconscious, eliminating, disabling, or producing | knock out | It is the phrasal verb. |
Further guidance
Core difference
The closed form functions as a noun or adjective; the open form expresses the action.
Fast Test
If you can say “knocked out” or “knocking out,” use the two-word verb.
Sense Boundary
Both forms have several established senses, so the reliable distinction is grammatical role rather than one narrow definition.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- KNOCKOUT — English meaning (opens in a new tab)Cambridge Dictionary · Noun and adjective meanings for closed “knockout”
- KNOCK OUT — English meaning (opens in a new tab)Cambridge Dictionary · Phrasal-verb meanings for “knock out”