Wingnut is a type of fastener, typically used to secure two objects together. It is a nut with two large metal wings on either side, which makes it easy to tighten and loosen by hand. The term 'wingnut' is also sometimes used as a slang term for someone who holds extreme or unorthodox political views. The crossword solution for the term wingnut is 'SCREWBALL', which is another type of fastener that is similar to a wingnut but has a rounded shape instead of wings.