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

• harden
• harshen
• strengthen
• toughen

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

Lucy’s Law, among other things, stiffens the penalties for seriously injuring someone in a boat crash. —David Goodhue, Miami Herald, 9 May 2025

Posture And Mobility: Undoing The Sedentary Spiral Extended sitting does more than stiffen your spine. —Ximena Araya-Fischel, Forbes.com, 19 Apr. 2025

The Padres’ 10-0 start at home is another franchise best, but at least on paper, the schedule will stiffen Monday when the Chicago Cubs — so far the only team to take a series against San Diego — visit Petco Park. —Dennis Lin, New York Times, 14 Apr. 2025

The city of Fort Worth has stiffened penalties for unauthorized tree clearing in an effort to hold developers accountable and protect the city’s natural landscapes. —Harrison Mantas, Fort Worth Star-Telegram, 23 Apr. 2025

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