also: やほー
A casual, friendly call used to get someone's attention or greet them in an informal setting. Often used when calling out to friends or in outdoor activities like hiking.
I shouted 'yoo-hoo' from the top of the mountain.
I spotted my friend and waved, saying 'hey!'
Likely a Japanese adaptation of the English 'yoo-hoo' or similar exclamation, used as a casual greeting or call.