The term 'Crazy One' can be described by three different crossword solutions: KOOK (4 letters), MANIAC (6 letters), and LOON (4 letters). KOOK is a slang term for someone who is eccentric or strange. MANIAC is a term used to describe someone who is mentally unstable or violent. Finally, LOON is an informal term for someone who is crazy or foolish. All three words are used to describe someone who is considered to be mentally unbalanced or irrational.