billow UK /ˈbɪl.əʊ/US /ˈbɪl.oʊ/verb 2noun 1forms 4 verb2 •To surge or roll in billows.The nuns' veils billowed and flapped behind the snaky line of girls as if the sisters were shooing the serpent from the Garden of Eden. — 1942 •To swell out or bulge.She had changed her auburn hair. Instead of wearing it in a billowing puff over her brow, she had gathered it into a ponytail, secured with a length of yellow yarn. — 1983 noun1 •A large wave, swell, surge, or undulating mass of something, such as water, smoke, fabric or sound.The snow fell hissing in the brine, / And the billows frothed like yeast. — 1842 formsbillowed · billowing · billoweth · billows