|Noah Webster's Dictionary|
1. (n.) A great wave or surge of the sea or other water, caused usually by violent wind.
2. (n.) A great wave or flood of anything.
3. (v. i.) To surge; to rise and roll in waves or surges; to undulate.
Int. Standard Bible Encyclopedia
bil'-o (gal, "a great rolling wave"): Figuratively, of trouble, "All thy waves and thy billows are gone over me" (Psalm 42:7; compare Jonah 2:3).
Billow (1 Occurrence)
Luke 21:25 "There will be signs in sun, moon, and stars; and on earth anguish among the nations in their bewilderment at the roaring of the sea and its billows; (Root in WEY ASV YLT)