SHRILLEST is a playable word

shrill Scrabble® Dictionary

adjective
shriller, shrillest
having a high-pitched and piercing quality
(adverb) shrilly
verb
shrilled, shrilling, shrills
to utter a shrill sound
250 Playable Words can be made from "SHRILLEST"
   2-Letter Words (15 found)
   8-Letter Words (2 found)
   9-Letter Words (1 found)