NUTSO is a slang term used to describe someone who is acting in an irrational or unpredictable manner. The crossword solutions for this term include LOON (4 letters), LOCO (4 letters), LOOPY (5 letters), MAD (3 letters), BATTY (5 letters), KOOK (4 letters), SCREWY (6 letters), COCKAMAMIE (10 letters), WACKY (5 letters), CRAZY (5 letters), and WACKEDOUT (9 letters). All of these words are synonyms for NUTSO and can be used to describe someone who is behaving erratically.