The phrase 'no stone unturned' is an idiom that means to LEAVE no possibility unexplored. It is often used to describe someone who is thorough and diligent in their search for a solution or answer. The crossword solution for this phrase is 'LEAVE', which is a verb meaning to go away from a place or situation. Therefore, the phrase 'no stone unturned' can be summarized as 'thoroughly exploring all possibilities before departing'.