koku-koku
Nodding one's head up and down repeatedly, often in agreement or while dozing off. A gentle, rhythmic motion.
💡A student falling asleep in class — 'She was koku-koku nodding off during the lecture.'
彼女は先生の話にこくこくとうなずいた。
She nodded koku-koku in agreement with the teacher.
The child ___ nodded along as grandpa told the story.
おじいちゃんの話に子どもが○○とうなずいた。