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

But one of the positives Glenn highlighted was the defense stiffening in the red zone against Chicago, which went 2 of 7 inside the New York 20-yard line. — ABC News, 5 Oct. 2026

Avoiding harsh chemicals like bleach, fabric softeners, and the like will help keep your robe soft and absorbent as these formulas could break down the fabric, leave behind fabric-stiffening residue, or cause pilling and other concerns. — Patricia Shannon, Southern Living, 26 Sep. 2026

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

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