halloo

Short definition from Wiktionary

Interjection

1. 1
   Used to greet someone, or to catch their attention.
2. 2
   Used in hunting to urge on the pursuers.

Noun

1. 1
   A shout of halloo.

Verb

1. 1
   To shout halloo.
2. 2
   To encourage with shouts; to egg (someone) on.
3. 3
   To chase with shouts or outcries.
4. 4
   To call or shout to; to hail.
5. 5
   To shout (something).