FASTEST is a playable word

fast Scrabble® Dictionary

adjective
faster, fastest
moving or able to move quickly
verb
fasted, fasting, fasts
to abstain from eating
96 Playable Words can be made from "FASTEST"
   2-Letter Words (10 found)
   3-Letter Words (25 found)
   6-Letter Words (6 found)
   7-Letter Words (1 found)