The term 'WHAT X MAY STAND FOR' can be answered by two crossword solutions: TEN (3 letters) and EXTRA (5 letters). TEN is a number that is used to represent the quantity of something, usually in the form of counting. It is the base of the decimal system and is used in many different contexts. EXTRA is an adjective that is used to describe something that is more than what is expected or necessary. It is often used to describe something that is additional or surplus.