Are You Sure? is a common phrase used to express doubt or disbelief. It is often used as a rhetorical question to challenge the validity of a statement or opinion. The two crossword solutions for this phrase are REALLY (6 letters) and ISIT (4 letters). REALLY is an adverb that means 'in fact' or 'TRULY'. ISIT is an informal contraction of 'is it'. Both words can be used to express doubt or disbelief, but they are not as commonly used as the phrase Are You Sure?