billow

American  

[bil-oh] / ˈbɪl oʊ /

noun

1. a great wave or surge of the sea.

   Synonyms:

   whitecap, roller, comber, breaker, swell

2. any surging mass.

   billows of smoke.

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verb (used without object)

1. to rise or roll in or like billows; surge.

2. to swell out, puff up, etc., as by the action of wind.

   flags billowing in the breeze.

verb (used with object)

1. to make rise, surge, swell, or the like.

   A sudden wind billowed the tent alarmingly.

billow British  

/ ˈbɪləʊ /

noun

1. a large sea wave

2. a swelling or surging mass, as of smoke or sound

3. a large atmospheric wave, usually in the lee of a hill

4. poetic (plural) the sea itself

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verb

1. to rise up, swell out, or cause to rise up or swell out

Other Word Forms

• billowing adjective
• underbillow verb (used without object)

Etymology

Origin of billow

First recorded in 1545–55; from Old Norse bylgja “wave,” cognate with Middle Low German bulge; akin to Old English gebylgan “to anger, provoke”

Explanation

Something billows when there's a fluid or blowing motion, such as the air filling a curtain at an open window, or smoke billowing from a fire. This word originally meant a wave, and that image should help you remember its current meaning too. The word usually suggests movement and growth, such as waves building and crashing. There are certain clouds that look like ocean waves, and so are called billow clouds. If you have a big shirt, the wind might make it fill with air and billow. Balloons are billowed when you inflate them. Billowing can also mean to move with difficulty — slowly.

Example Sentences

There’s nothing like watching as clouds billow over Doi Suthep, the mountain overlooking Chiang Mai, before gushing onto the city’s durian- and diesel-fumed streets.

From The Wall Street Journal • Jan. 28, 2026

On the morning of Sept. 11, 2001, I was in northern New Jersey, and watched the smoke billow from the World Trade Center.

From Slate • Oct. 29, 2025

When the winds got especially fierce, like they did last week, smoke would billow back down the chimney and fill the living room.

From Los Angeles Times • Jan. 12, 2025

Aromatic plumes billow out from aluminum-covered vent hoods as chefs with decades of experience produce steaming plates of crackled shrimp, juicy mussels, and crisped-up rice by tossing the ingredients in a giant, flame-cradled wok.

From Salon • May 15, 2024

Up above, clouds will billow out of nowhere into dark monstrosities, pregnant with malevolent intent, and a clear blue sky is like a magnifying glass for a punishing sun.

From "Challenger Deep" by Neal Shusterman

Related Words

• undulate