hollo

(noun) a very loud utterance (like the sound of an animal). Synonyms: bellow, bellowing, holla, holler, hollering, holloa, roar, roaring, yowl. Example: "His bellow filled the hallway."

(verb) encourage somebody by crying hollo.

(verb) cry hollo.

(verb) utter a sudden loud cry. Synonyms: shout, shout out, cry, call, yell, scream, holler, squall. Examples: "She cried with pain when the doctor inserted the needle." "I yelled to her from the window but she couldn't hear me."