To shout in a loud voice, or (of a cow or large animal) to make a loud, deep sound. (Cambridge Dictionary)
(of a person or animal) emit a deep loud roar, typically in pain or anger. (Oxford Dictionaries)
An instrument or machine that by alternate expansion and contraction draws in air through a valve or orifice and expels it through a tube. (Merriam – Webster)
If someone bellows, they shout angrily in a loud, deep voice. (Collins Dictionary)
Pleasant Hearth. Fireplace Bellow.
Bellow. Red Deer. Flickr.