noun
killer
KIH-luh
noun
1
A person or animal that kills, especially one who murders someone.
"Police are still searching for the killer."
adj
1
Extremely impressive, excellent, or effective.
"She played a killer set at the festival."
"That was a killer presentation — well done."
How to Use Killer
Learner’s notesIn plain EnglishSomeone who kills, or (informally) something outstandingly good or difficult.
When to use it
The "excellent" sense is informal slang, common in casual speech.
Common pairings
serial killer
killer instinct
killer app
Word Forms
more killer comparative, killers plural, most killer superlative
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Etymology
From Middle English "killer/kyller," formed from "kill" + the agent suffix "-er."