RILLS is a playable word

rill Scrabble® Dictionary

verb
rilled, rilling, rills
to flow like a rill (a small brook)
11 Playable Words can be made from "RILLS"
   2-Letter Words (3 found)
   3-Letter Words (4 found)
   4-Letter Words (3 found)
   5-Letter Words (1 found)