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

Michael Carroll’s son stiffened — a cold jolt running through him — when his shovel struck what looked like rags and bones in the basement on Halloween eve 2018. —Stephanie Nolasco, FOXNews.com, 13 Dec. 2025

Here, it is mated to a six-speed manual transmission, and the suspension has been stiffened a little for a sportier feel. —Erik Shilling, Robb Report, 8 Dec. 2025

The Broncos' defense stiffened in the fourth quarter yet again, but finally bent at the end of regulation in surrendering a game-tying field-goal drive. —Luca Evans, Denver Post, 1 Dec. 2025

However, New Jersey Congressman Josh Gottheimer is trying to stiffen penalties for those who get arrested by introducing legislation called the Porch Pirates Act. —Nick Caloway, CBS News, 1 Dec. 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