General:
* Slow
* Lethargy
* Inert
* Inactive
* Dull
* Languid
* Listless
* Unresponsive
More specific:
* For movement: Torpid, ponderous, sluggish
* For economy: Stagnant, recessionary, depressed
* For mental state: Drowsy, apathetic, lethargic
Informal:
* Lazy
* Slowpoke
* Draggy
The best synonym will depend on the specific meaning you want to convey.
