The term 'unexcelled' can be broken down into three crossword solutions: BEST (4 letters), ALONE (5 letters), and SECONDTONONE (12 letters). BEST is an adjective meaning of the highest quality or most excellent, ALONE is an adjective meaning having no one else present, and SECONDTONONE is an adjective meaning being the BEST of its kind. Taken together, these three words describe something that is of the highest quality, with no one else present, and the BEST of its kind.