The term 'flip-side' is used to refer to the opposite or REVERSE side of something. In this case, the crossword solutions for the term are 'REVERSE' (7 letters) and 'TAILS' (5 letters). The term 'REVERSE' implies that the flip-side is the exact opposite of the original, while 'TAILS' is often used to refer to the back side of a coin. Therefore, the two solutions together suggest that the flip-side of something is its exact opposite, like the other side of a coin.