The Collaborative International Dictionary of English v.0.48:
Roar \Roar\, v. i. [imp. & p. p. Roared; p. pr. & vvb. n.
Roaring.] [OE. roren, raren, AS. r[=a]rian; akin to G.
r["o]hten, OHG. r[=e]r[=e]n. [root]112.]
1. To cry with a full, loud, continued sound. Specifically:
(a) To bellow, or utter a deep, loud cry, as a lion or
Roaring bulls he would him make to tame.
(b) To cry loudly, as in pain, distress, or anger.
Sole on the barren sands, the suffering chief
Roared out for anguish, and indulged his grief.
He scorned to roar under the impressions of a
finite anger. --South.
2. To make a loud, confused sound, as winds, waves, passing
vehicles, a crowd of persons when shouting together, or
The brazen throat of war had ceased to roar.
How oft I crossed where carts and coaches roar.
3. To be boisterous; to be disorderly.
It was a mad, roaring time, full of extravagance.
4. To laugh out loudly and continuously; as, the hearers
roared at his jokes.
5. To make a loud noise in breathing, as horses having a
certain disease. See Roaring, 2.
Roaring boy, a roaring, noisy fellow; -- name given, at the
latter end Queen Elizabeth's reign, to the riotous fellows
who raised disturbances in the street. "Two roaring boys
of Rome, that made all split." --Beau. & Fl.
Roaring forties (Naut.), a sailor's name for the stormy
tract of ocean between 40[deg] and 50[deg] north latitude.