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 United States and its allies must strive to stiffen the security of their military research, production, and supply chains. — Sam Mullins, Foreign Affairs, 28 Oct. 2026

However, for someone with a preexisting condition such as pulmonary fibrosis – where the tissue of the lungs has stiffened and can no longer stretch to full capacity – a viral infection may make their condition worse. — Karin Wuertz-Kozak, The Conversation, 27 Oct. 2026

Texas stiffened and took the 21-point lead to the locker room. — ABC News, 24 Oct. 2026

If the washer cannot rinse all of it away, the residue can stiffen the fibers and attract additional soil. — Ashlyn Needham, Southern Living, 24 Oct. 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