A topcoat is an outer layer of clothing worn over other clothes to provide warmth and protection from weather. When you see someone wearing a long coat over their sweater and pants on a cold day, that's a topcoat. The name makes sense: it's literally the top layer, the coat that goes on top of everything else.

Topcoats are usually made from heavier fabrics like wool or thick cotton, and they're designed to keep out wind and cold without being as heavy as a winter parka. A businessperson might wear a topcoat over a suit, while a student might throw one on over jeans and a hoodie before heading to school on a chilly morning.

The word also has a technical meaning in painting and finishing work. When painters apply a topcoat, they're adding the final protective layer over earlier coats of paint. This top layer gives the surface its final color and shine while protecting the layers underneath. A furniture maker might sand a wooden table smooth, apply a stain, and then finish with a clear topcoat that makes it glossy and protects it from spills and scratches.