The term 'unimportant matter' can be summarized by two crossword solutions: 'nonissue' (8 letters) and 'TRIFLE' (6 letters). Both terms refer to something that is of little or no importance, and can be used to describe a situation or event that is not worth worrying about. Nonissue implies that the matter is so insignificant that it is not even worth discussing, while TRIFLE suggests that the matter is trivial and inconsequential.