stiffen

verb

stiff·​en ˈsti-fən 

stiffened; stiffening ˈsti-fə-niŋ 

ˈstif-niŋ

transitive verb

: to make stiff or stiffer

intransitive verb

: to become stiff or stiffer

stiffener

ˈsti-fə-nər 

ˈstif-nər

noun

Synonyms of stiffen

• strengthen

Examples of stiffen in a Sentence

She stiffened when he grabbed her shoulder.

The dogs stiffened in alarm.

The law would stiffen penalties for tax evasion.

Recent Examples on the Web

Davidsen bucks up her balky husband with a bloodthirsty holler, stiffens her voice against doubt, and, in her final sleepwalking scene, taps into the tender stratum of Lady Macbeth’s subconscious. — Justin Davidson, Vulture, 23 Sep. 2026

The Chiefs’ defense stiffened and Indy faced a fourth-and-8 from the 15-yard line. — Pete Grathoff, Kansas City Star, 21 Sep. 2026

Over time, smoking can narrow and stiffen blood vessels and accelerate cardiovascular disease. — Katia Hetter, CNN Money, 16 Sep. 2026

But after a quick touchdown drive to take a 34-27 lead, the Oregon defense stiffened, and closed out the win with back-to-back stops. — Ian Miller Outkick, FOXNews.com, 6 Sep. 2026

Word History

First Known Use

15th century, in the meaning defined at transitive sense

Rhymes for stiffen

• griffon
• gryphon
• tiffin

Kids Definition

stiffen

verb

stiff·​en ˈstif-ən 

stiffened; stiffening -(ə-)niŋ 

: to make or become stiff or stiffer

stiffener

-(ə-)nər 

noun