[bil.low] n [ON bylgja; akin to OHG balg bag--more at belly] (1552) 1: wave; esp: a great wave or surge of water
2: a rolling mass (as of flame or smoke) that resembles a high wave -- bil.lowy adj
[2]billow vi (1597) 1: to rise or roll in waves or surges
2: to bulge or swell out (as through action of the wind) ~ vt: to cause to billow