Yes, SHORTER is a Scrabble word!

adjective

1. primarily temporal sense; indicating or being or seeming to be limited in duration
2. (primarily spatial sense) having little length or lacking in length
3. low in stature; not tall
4. not sufficient to meet a need
5. (of memory) deficient in retentiveness or range
6. not holding securities or commodities that one sells in expectation of a fall in prices
7. of speech sounds or syllables of relatively short duration
8. less than the correct or legal or full amount often deliberately so
9. lacking foresight or scope
10. tending to crumble or break into flakes due to a large amount of shortening
11. marked by rude or peremptory shortness