UNKNOWN is a playable word

unknown Scrabble® Dictionary

noun
pl. unknowns
one that is not known
18 Playable Words can be made from "UNKNOWN"
   2-Letter Words (7 found)
   3-Letter Words (5 found)
   4-Letter Words (3 found)
   5-Letter Words (2 found)
   7-Letter Words (1 found)