General synonyms:
* Sleeping
* Dozing
* Resting
* Napping
* Snoozing
* Drowsing
More poetic synonyms:
* Reposing
* Reclining
* Slumbering
* Dormant
* Asleep
Synonyms emphasizing a lack of activity:
* Inactive
* Quiescent
* Latent
* Still
* Unresponsive
Synonyms emphasizing a temporary state:
* Awaiting
* Holding back
* In abeyance
* Suspended
The best synonym will depend on the specific situation and the tone you want to convey.