General:
* Back
* Rear
* Hind
* Behind
* Dorsal (in anatomical context)
More formal:
* Caudal (anatomical, referring to the tail end)
* Dorsad (anatomical, meaning "towards the back")
Figurative:
* Following
* Subsequent
* Later (when referring to time)
The best synonym will depend on the specific meaning you want to convey.