The term SUNROOF ALTERNATIVE can be summarized by two crossword solutions: TOP (3 letters) and TTOP (4 letters). TOP is an acronym for 'Targa TOP, ' which is a type of removable roof panel that is often used as an alternative to a sunroof. TTOP stands for 'Transparent TOP, ' which is a type of removable roof panel that is made of transparent material, such as glass or plastic, and is also used as an alternative to a sunroof.