Definition of "halloo" []

• Used to catch someone's attention. (interjection)
• Used to urge on hounds in a hunt. (interjection)
• A shout or call of "halloo.” (noun)
• To shout "halloo.” (verb-intransitive)
• To urge on or pursue by calling "halloo” or shouting. (verb-transitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Then I hallooed, first making sure that there was no one lurking near to overhear, and waved my handkerchief, keeping my horse standing to his fetlocks in the current, until over the water came an answering halloo from the Golden Horn, and I could plainly see Captain Calvin Tabor on the quarter-deck."
• "Sophie acknowledged the fact with a grimace as, with a wave and a whooping "halloo," Clarissa shot past."
• "One might "halloo" to an old acquaintance forty rods distant, down a country lane; but on Broadway he bows only to the ones whom he meets point blank."