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

The moose flinched and stiffened. — Fred Bear, Outdoor Life, 11 June 2026

Nicks on the edge or stiffened, curled rubber will leave streaks. — Mary Marlowe Leverette, Southern Living, 12 June 2026

Group 1 is pulmonary arterial hypertension, a rare and severe version that occurs when blood vessels in the lungs narrow and stiffen. — Elizabeth Cooney, STAT, 26 June 2026

To execute its ruthless 66-pound weight loss program, the rear seats have been completely deleted, replaced by a massive structural strut brace that significantly stiffens the chassis. — Peter Lyon, Forbes.com, 13 June 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