flatten

verb

flat·​ten ˈfla-tᵊn 

flattened; flattening ˈflat-niŋ 

ˈfla-tə-

transitive verb

: to make flat: such as

a

: to make level or smooth

b

: to knock down

also : to defeat decisively

c

: to make dull or uninspired

—often used with out

d

: to make lusterless

flatten paint

e

: to stabilize especially at a lower level

intransitive verb

: to become flat or flatter: such as

a

: to become dull or spiritless

b

: to extend in or into a flat position or form

c

: to become uniform or stabilized often at a new lower level

—usually used with out

flattener

ˈflat-nər 

ˈfla-tə-

noun

Synonyms

• smooth

Examples of flatten in a Sentence

Dozens of houses were flattened by the tornado.

The boxer was flattened in the seventh round.

The team got flattened in the first round of the play-offs.

Prices are expected to flatten after the holiday shopping season.

Recent Examples on the Web

In the early sections, the author’s wry voice never flattens the meringue tips of Ruth’s childlike wonder. —Book Marks august 22, Literary Hub, 22 Aug. 2025

Gently press down on the meatballs with a spatula to slightly flatten them. —Lynda Balslev, Mercury News, 15 Aug. 2025

Retail returns are not rising—the downtrend that began in 2022 has merely flattened, while deposit balances remain above 2019 levels even after adjusting for inflation, and credit card borrowing habits remain healthier than pre-pandemic. —Emma Burleigh, Fortune, 13 Aug. 2025

While suona reeds are traditionally plant-based, Zhen flattens segments of plastic straws to fit into his mouthpiece. —William Tong, Chicago Tribune, 7 Aug. 2025

Word History

First Known Use

1630, in the meaning defined at transitive sense

Rhymes for flatten

• batten
• craton
• fatten
• gratin
• gratton
• latin
• lattin
• matin
• paten
• patten
• platen
• ratan

Kids Definition

flatten

verb

flat·​ten ˈflat-ᵊn 

flattened; flattening ˈflat-niŋ 

-ᵊn-iŋ

: to make or become flat