billow

/ˈbɪloʊ/

/ˈbɪləʊ/

Other forms: billows; billowing; billowed

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.

Definitions of billow

1. noun

   a large sea wave
   synonyms: surge

   type of:

   moving ridge, wave

   one of a series of ridges that moves across the surface of a liquid (especially across a large body of water)
2. verb

   rise up as if in waves
   “smoke billowed up into the sky”

   synonyms: wallow

   types:

   cloud

   billow up in the form of a cloud

   type of:

   soar, soar up, soar upwards, surge, zoom

   rise rapidly
3. verb

   rise and move, as in waves or billows
   synonyms: heave, surge

   type of:

   blow up, inflate

   fill with gas or air
4. verb

   move with great difficulty
   “The soldiers billowed across the muddy riverbed”

   type of:

   go, locomote, move, travel

   change location; move, travel, or proceed, also metaphorically
5. verb

   become inflated
   synonyms: balloon, inflate

   types:

   reflate

   become inflated again

   type of:

   expand

   become larger in size or volume or quantity