According to Osho, Yaa-Hoo! has no dictionary meaning; it is an existential sound-key: Hoo (from Sufi practice) strikes the very center, silencing mind and time, while Yaa adds joy, laughter, and dance. Together they invoke a celebrative, centered awareness—the laughing, dancing being—and serve as a powerful meditative trigger to cleanse repression and open inner space.
It’s a happy shout that quiets your mind and wakes up your joyful self so you feel like laughing and dancing.