The term 'YOU CAN'T BE SERIOUS!' is an expression of disbelief or incredulity. It is often used when someone is shocked or surprised by something that has been said or done. The crossword solutions for this term include CMON (4 letters), NOWAY (5 letters), OHMAN (5 letters), GETREAL (7 letters), OHCOMEON (8 letters), PUHLEEZE (8 letters), THATSALAUGH (11 letters), AREYOUKIDDINGME (15 letters), DONTMAKEMELAUGH (15 letters), IDONTBELIEVEYOU (15 letters), and YOUMUSTBEJOKING (15 letters). All of these solutions are expressions of disbelief or incredulity, and they all convey the same sentiment as the original phrase.