I. bil ‧ low 1 /ˈbɪləʊ $ -loʊ/ BrE AmE verb [intransitive]
1 . ( also billow out ) if something made of cloth billows, it moves in the wind:
Her long skirt billowed in the breeze.
2 . if a cloud or smoke billows, it rises in a round mass
billow out of/up etc
There was smoke billowing out of the windows.
II. billow 2 BrE AmE noun [countable usually plural]
[ Date: 1500-1600 ; Origin: Probably from Old Norse bylgja ]
1 . a moving cloud or mass of something such as smoke or cloth
2 . literary a wave, especially a very large one