interjection, noun, plural hal·loos, verb (used with or without object), hal·looed, hal·loo·ing.
Examples from the Web for halloo
It was remarked afterwards that the Squire had never been known to halloo to a fox in that way before.Ralph the Heir|Anthony Trollope
Ye clumps of buffalo grass, I tell you and send it to you that ye may hear it, halloo!
And away he ran among the trees in search of his pigs, while Eric heard his little drum, and his song of "Rub-a-dub, halloo!"The Gold Thread|Norman MacLeod
When I come, said he, I will halloo, and you must let me in.Alonzo and Melissa|Daniel Jackson, Jr.
All ye small animals, I tell you and send it to you that ye may hear it, halloo!