To make a hollow, loud noise, as an enraged bull.

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

To emit with a loud voice; to shout; -- used with out.

A loud resounding outcry or noise, as of an enraged bull; a roar.

a very loud utterance (like the sound of an animal); "his bellow filled the hallway"

shout loudly and without restraint

make a loud noise, as of animal; "The bull bellowed"

a long, loud call that travels quite far

The sound made by the Right Whale when in violent action. Since whales have no vocal cords, this sound comes from either the lungs or the abdomen.