GRUMBLE is a playable word

grumble Scrabble® Dictionary

verb
grumbled, grumbling, grumbles
to mutter in discontent
79 Playable Words can be made from "GRUMBLE"
   2-Letter Words (8 found)
   3-Letter Words (27 found)
   6-Letter Words (5 found)
   7-Letter Words (1 found)