いないいないばあalso: いないないばあMeanings1interjectionpeek-a-boo!A phrase used when playing peek-a-boo with a baby; said while hiding and then revealing one's face.赤あかちゃんに「いないいないばあ」をすると、大おお喜よろこびした。When I played peek-a-boo with the baby, she was delighted.