General synonyms:
* Wandering
* Itinerant
* Roving
* Migratory
* Peripatetic
* Traveling
* Errant
More specific synonyms:
* Pastoral (if referring to a lifestyle of herding animals)
* Seminomadic (if referring to a lifestyle that is partly nomadic)
* Transhumant (if referring to a seasonal migration of livestock)
The best synonym for "nomadic" will depend on the specific situation and the meaning you want to convey.