adjective
not used before a noun
in a state of sleep :sleeping
When people are fast asleep or sound asleep, they are sleeping very deeply.
If you are half asleep, you are very tired and not completely awake.
lacking any feeling
If a part of your body (such as a foot or leg) is asleep, it is not able to feel anything for a brief time, usually because you have kept it in an awkward position for too long.
fall asleep
to begin sleeping
US