Source : Webster's Revised Unabridged Dictionary (1913)

Bellow \Bel"low\, v. i. [imp. & p. p. {Bellowed}; p. pr. & vb.
   n. {Bellowing}.] [OE. belwen, belowen, AS. bylgean, fr.
   bellan; akin to G. bellen, and perh. to L. flere to weep,
   OSlav. bleja to bleat, Lith. balsas voice. Cf. {Bell}, n. &
   v., {Bawl}, {Bull}.]
   1. To make a hollow, loud noise, as an enraged bull.

   2. To bowl; to vociferate; to clamor. --Dryden.

   3. To roar; as the sea in a tempest, or as the wind when
      violent; to make a loud, hollow, continued sound.

            The bellowing voice of boiling seas.  --Dryden.

Bellow \Bel"low\, v. t.
   To emit with a loud voice; to shout; -- used with out.
   ``Would bellow out a laugh.'' --Dryden.

Bellow \Bel"low\, n.
   A loud resounding outcry or noise, as of an enraged bull; a
   roar.

Source : WordNet®

bellow
     n 1: a very loud utterance (like the sound of an animal); "his
          bellow filled the hallway" [syn: {bellowing}, {holla}, {holler},
           {hollering}, {hollo}, {holloa}, {roar}, {roaring}, {yowl}]
     2: United States novelist (born in Canada in 1915) [syn: {Saul
        Bellow}]

bellow
     v 1: shout loudly and without restraint [syn: {bawl}]
     2: make a loud noise, as of animal; "The bull bellowed" [syn: {roar}]