GRUMPIEST is a playable word

grumpy Scrabble® Dictionary

adjective
grumpier, grumpiest
ill-tempered
(adverb) grumpily
401 Playable Words can be made from "GRUMPIEST"
   2-Letter Words (20 found)
   3-Letter Words (80 found)
   8-Letter Words (3 found)
   9-Letter Words (1 found)