The crossword solution for the term 'buckle opening' is SWASH, which is a five-letter word. SWASH is a type of buckle opening that is used to fasten two pieces of material together. It is usually made of metal and consists of two parts, one with a protruding pin and the other with a hole for the pin to fit into. The SWASH buckle is often used in clothing, such as belts, and can also be used to secure items like backpacks or luggage.