HILLIEST is a playable word

hilly Scrabble® Dictionary

adjective
hillier, hilliest
abounding in hills
103 Playable Words can be made from "HILLIEST"
   2-Letter Words (13 found)
   3-Letter Words (27 found)
   6-Letter Words (5 found)
   7-Letter Words (1 found)
   8-Letter Words (1 found)