Yes, outer is a Scrabble word!

Adjective

1. Being on the outside or further from a center

2. Located outside

3. Being on or toward the outside of the body

4. Not allowed to continue to bat or run

5. Being out or having grown cold

6. Not worth considering as a possibility

7. Out of power; especially having been unsuccessful in an election

8. Excluded from use or mention

9. Directed outward or serving to direct something outward

10. No longer fashionable

11. Outside or external

12. Outer or outlying

13. Knocked unconscious by a heavy blow