The term 'SAY NO TO RUBBISH' can be summarized by the crossword solution 'REFUSE', which is a 6-letter word. REFUSE means TO deny or reject something, and in this context it is used TO express the idea of rejecting or not accepting something that is considered undesirable or unnecessary. This phrase is often used TO encourage people TO reduce their consumption of single-use plastics and other materials that are harmful TO the environment.