The term 'ART (RETRO STYLE)' can be summarized by the crossword solution DECO, which is a four-letter word. DECO is short for Art Deco, a style of visual arts, architecture, and design that first appeared in France during the 1920s. This style was characterized by its use of bold geometric shapes, bright colors, and luxurious materials. It was popularized in the 1930s and 1940s and has since become a classic retro style.