1. To fall asleep, usually briefly or when one is not mean to. I was so tired from staying up all night that I kept nodding out throughout the day.

2. To enter a euphoric state between consciousness and unconsciousness as a result of drug use, especially heroin or opioids. We all just got our fix and nodded out in the living room. I noticed his skin turning blue after he nodded out, so I called an ambulance.