Source : Webster's Revised Unabridged Dictionary (1913)

Holloa \Hol*loa"\, interj., n. & v. i.
   Same as {Hollo}.

Source : WordNet®

holloa
     n : a very loud utterance (like the sound of an animal); "his
         bellow filled the hallway" [syn: {bellow}, {bellowing}, {holla},
          {holler}, {hollering}, {hollo}, {roar}, {roaring}, {yowl}]