1. To dance, sway, or sing along very enthusiastically to some music, especially rock and roll. My dad always embarrasses me so much when he starts rocking to AC/DC in the car. I've never seen anyone rock to Mozart like that before.

2. To cause or help someone to fall asleep by moving them back and forth or side to side in a gentle, rhythmic motion. In this usage, a noun or pronoun is used between "rock" and "to." I've been trying to rock the baby to sleep for hours now, but she just won't settle. He held his sick husband in his arms and rocked him to sleep.