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

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

Softening rather than stiffening when moving through space requires embracing your body’s natural sway and tiny micro-movements, like an ankle wobbling or knee jiggling. — Deborah Vankin, Los Angeles Times, 18 Aug. 2026

Not to mention their unusually flexible blood vessels could also help compensate for stiffening heart tissue. — Melissa Cristina Márquez, Forbes.com, 1 Aug. 2026

Even simple movements can encourage healthy blood flow and keep fascia from stiffening up. — Jennifer Heimlich, Time, 27 July 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