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

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

Bile rose in Evie’s throat and her body stiffened under his touch. — Literary Hub, 2 Sep. 2026

Offering a 35% incentive aimed at stiffening up jobs here and enticing post-production to relocate to the Golden State, AB 2319 is racing toward a vote in the state Senate by next week once the bill is in final shape. — Dominic Patten, Deadline, 20 Aug. 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