Source : Webster's Revised Unabridged Dictionary (1913)

Billow \Bil"low\, v. i. [imp. & p. p. {Billowed}; p. pr. & vb.
   n. {Billowing}.]
   To surge; to rise and roll in waves or surges; to undulate.
   ``The billowing snow.'' --Prior.

Source : WordNet®

billowing
     adj 1: moving in surges and billows and rolls; "billowing smoke
            from burning houses"; "the rolling fog"; "the rolling
            sea"; "the tumbling water of the rapids" [syn: {rolling},
             {tumbling}]
     2: characterized by great swelling waves or surges; "billowy
        storm clouds"; "the restless billowing sea"; "surging
        waves" [syn: {billowy}, {billowing(a)}, {surging}]