The term 'FOREIGN LEGION HEADWEAR' can be summarized by the crossword solution 'KEPI', which is a four-letter word. KEPI is a French word for a type of cap that was originally worn by the French Foreign Legion. It is a stiff, round cap with a flat top and a visor, and is usually made of wool or cotton. The KEPI has become an iconic symbol of the French Foreign Legion, and is still worn by its members today.