The term 'past its best' can be described by two crossword solutions: 'OVERRIPE' (8 letters) and 'STALE' (5 letters). OVERRIPE refers to food that has been left too long and has become soft, discolored, and sometimes moldy. STALE is a term used to describe food that has been left out for too long and has lost its flavor and texture. Both terms indicate that the food has gone past its prime and is no longer at its best.