A plume is a large, showy feather or group of feathers, especially the kind that stands out because of its size, shape, or bright colors. Knights in medieval times wore plumes on their helmets to look impressive in tournaments. Some fancy hats feature tall ostrich plumes that wave dramatically when the wearer moves. Male peacocks display magnificent plumes to attract mates, fanning out their iridescent tail feathers in a spectacular show.

The word also describes anything that spreads out in a shape similar to a large feather. When a volcano erupts, it sends up a plume of smoke and ash that rises high into the sky and spreads out at the top. A factory smokestack releases a plume of steam. When you see your breath on a cold morning, you're creating tiny plumes of water vapor. Scientists track plumes of pollution in the ocean or atmosphere to understand how contaminants spread through the environment.

As a verb, plume can mean to smooth and arrange feathers with the beak. You might hear someone say a bird plumes itself, making its feathers look neat and attractive.