The Collaborative International Dictionary of English v.0.48:
Bellower \Bel"low*er\, n. One who, or that which, bellows. [1913 Webster]WordNet (r) 3.0 (2006):
bellower n 1: someone who communicates vocally in a very loud voice [syn: roarer, bawler, bellower, screamer, screecher, shouter, yeller]