WordWeb Online

1. A shout to attract attention
   "he gave a great halloo but no one heard him"

1. Urge on with shouts
   "halloo the dogs in a hunt"
    
2. Shout 'halloo', as when greeting someone or attracting attention

Derived forms: hallooed, hallooing, halloos

Type of: call, cry, egg, egg on, holler, hollo [non-standard], incite, outcry, prod, scream, shout, shout out, squall, vociferation, yell