The term 'THAT'S ___ NONSENSE!' can be completed with the crossword solutions UTTER (5 letters), PISH (4 letters), TUSH (4 letters), HOOEY (5 letters), and MYEYE (5 letters). These words are all slang terms used to express disbelief or disagreement. UTTER means complete or absolute, pish is an expression of contempt or disapproval, TUSH is a milder version of pish, HOOEY is an exclamation of disbelief, and myeye is an expression of disbelief or doubt. All of these words can be used to express disbelief in response to something that is considered nonsense.