The term 'REMAINED UNUSED' can be broken down into two crossword solutions: SAT (3 letters) and WENTTOWASTE (11 letters). SAT stands for 'Scholastic Aptitude Test', which is a standardized test used to measure a student's readiness for college. WENTTOWASTE is an idiom meaning that something has been wasted or not used to its full potential. Together, the two solutions indicate that something has not been utilized to its fullest extent.