1. Overworked or exhausted, especially to the point of no longer being able to maintain a particular level of performance or dedication. If you keep working nights and weekends, you're going to get burned out. She's probably burned out after studying all week.

2. slang Physically damaged by drug use. Typically used to describe an IV drug user's veins. I used to be an addict, honey, so my veins are all burned out these days.

3. slang Negatively impacted by drug use or addiction. You can't just dismiss these burned out students when they clearly need help and guidance.

4. slang Tolerant of a certain drug and thus unable to feel its effects anymore. I'm burned out on that stuff, man—it just does nothing for me anymore.