Blankety-blank is a term used to describe something that is not specified or left blank. It is often used in crosswords, where the answer is not known and the puzzle solver must fill in the blank. The term can also be used to describe a situation where something is missing or unknown. In this case, the crossword solution for the term Blankety-blank is 'darned', which is a verb meaning to mend or repair something with stitches.