Definition from Wiktionary, the free dictionary
- (nautical) Used to hail a ship, a boat or a person, or to attract attention.
- 1751: While he was thus occupied, a voice, still more uncouth than the former, bawled aloud, ‘Ho! the house, a-hoy!’, The Adventures of Peregrine Pickle, Tobias Smollett.
Usage notes 
- Traditionally, when used from a ship to hail an approaching boat, the standard responses are:
Derived terms 
used to hail a ship, etc
- To hail with a cry of "ahoy".