To sunbathe means to sit or lie outside in the sunshine, usually to relax or to make your skin darker. People sunbathe at the beach, by the pool, or in their backyards, soaking up the sun's warmth and light.

When someone sunbathes, they're deliberately exposing their skin to sunlight, often while wearing swimsuits or summer clothes. Cats are expert sunbathers: you'll find them sprawled in sunny patches on the floor, completely content. Turtles sunbathe on logs and rocks to warm their bodies, since they're cold-blooded and need the sun's heat to regulate their temperature.

People have sunbathed for centuries, though we now know that too much sun exposure can damage skin, so most people today use sunscreen and limit their time in the sun when sunbathing. You might hear someone say they're going to “catch some rays” or “work on their tan,” which both mean essentially the same thing as sunbathing.