滑 has three core uses. As an adjective for slippery surfaces, it contrasts with 光滑, which emphasizes a smooth, glossy texture. As a figurative adjective meaning sly, it is less strong and less formal than the derogatory 狡猾. As a verb, 滑 is the general action; compounds like 滑冰, 滑行, and 下滑 specify particular ways of sliding.