1. (of fabric) fill with air and swell outward: "her dress billowed out around her"Similarpuff up/outballoon (out)swellfill outbulge outbelly out
▪ (of smoke, cloud, or steam) move or flow outward with an undulating motion:"smoke was billowing from the chimney"Similarpourflowswirlspiralrollundulaterise and falleddy
Word Originmid 16th century: from Old Norse bylgja.