Used to call someone at a distance or to gain someone's attention.(interjection)
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.
Use "yoo-hoo" in a sentence
"I feel I should somehow stick my hand up and say, yoo-hoo, me again, Litlove talking."
"Then a neighbour would call out Hi, yoo-hoo, anyone there? and my partner would suddenly abandon her scowl and cheerily discuss the latest episode of Buffy the Vampire Slayer."
"Well-said and another true meaningful yoo-hoo for your 'lil light Lulu."