Asleep means being in a state where you rest and don't think about anything consciously.
You've probably gone asleep many times before, like when you're tired after a long day or a busy week. When someone says "I was asleep on the couch," it usually means they were sitting there but dozing off, not paying attention to their surroundings. This can happen if they're watching TV, listening to music, or just relaxing. It's common for people to fall asleep while doing things that are supposed to be boring, like waiting in line or reading a book on a bus ride.
In a state of sleep; also, broadly, resting.
Example: I was asleep when you called.
