killer

1 of 2

noun

kill·​er ˈki-lər 

1

: one that kills

2

: killer whale

3

a

: one that has a forceful, violent, or striking impact

b

: one that is extremely difficult to deal with

killer

2 of 2

adjective

1

: strikingly impressive or effective

a killer smile

a killer résumé

2

: extremely difficult to deal with

a killer fastball

also : causing death or devastation

a killer tornado

Synonyms of killer

Noun

• headache
• job

Adjective

• lethal
• deadly
• fatal

Examples of killer in a Sentence

Noun

Heart disease is the leading killer of both men and women.

The chemical is used as a weed killer.

Adjective

killer viruses that claimed millions of lives

a killer exercise program guaranteed to whip you into shape

Recent Examples on the Web

Noun

Fertilizers, weed killers and pesticides sit right where your dog sniffs and walks. — Ryan Brennan, Kansas City Star, 2 July 2026

Mayhem comes to a coastal New England town in the form of a killer shark who hunts anybody dumb enough to get in the water. — Brian Truitt, USA Today, 1 July 2026

The upshot is that plaintiffs can’t sue the biotech company for not putting a cancer warning on the label of Roundup, the popular weed killer. — Zachary Karabell, Washington Post, 1 July 2026

Because dogs stay low and sniff constantly, fertilizers, weed killers and insecticides reach them easily. — Ryan Brennan, Miami Herald, 2 July 2026

Word History

First Known Use

Noun

15th century, in the meaning defined at sense 1

Adjective

1939, in the meaning defined at sense 2

Phrases Containing killer

• killer app
• killer bee
• killer cell
• killer instinct
• killer T cell
• killer T lymphocyte
• killer whale
• lady-killer
• natural killer cell
• pain-killer
• time killer

Rhymes for killer

• biller
• chiller
• driller
• filler
• hilar
• hiller
• pillar
• quiller
• siller
• spiller
• stiller
• thriller

Kids Definition

killer

1 of 2 noun

ˈkil-ər

1

: one that kills

2

: killer whale

killer

2 of 2 adjective

1

: strikingly impressive or effective

a killer smile

2

: extremely difficult

a killer exam

also : causing death or devastation

a killer tornado