Etymology

Interjection

1. A variant of hello
2. A cry of surprise.
   • 1890, Sir Arthur Conan Doyle, The Sign of the Four,

     It sounds like a sum in the rule of three. The answer should give us the — But hallo! here are the accredited representatives of the law.

Verb

1. To shout, or to call with a loud voice.
2. To chase while shouting "hallo!"
3. To cry "hallo" (to someone).
4. To shout (something).