Window coating is a type of protective covering that is applied to the exterior of windows to protect them from the elements. The two crossword solutions for the term window coating are HOAR and FROST, both of which refer to the white, icy deposits that form on the outside of windows in cold weather. HOAR is a four-letter word meaning 'covered with white FROST, ' while FROST is a five-letter word meaning 'a layer of tiny ice crystals formed on the ground or other surfaces.'