If something is obscure, it's vague and hard to see. Be careful if you're driving in heavy rain — the painted lines can be obscure.
Obscure comes from Latin obscurus, which can mean "dark, dim," "unclear, hard to understand," or "insignificant, humble." We tend to use obscure in the metaphorical senses: an obscure sound is unclear, an obscure village is hidden away in the countryside, and an obscure poet is little known and probably insignificant. Obscure can also be used as a verb. If you get really nervous when you speak during a debate, your embarrassing twitches and shaking hands can obscure your argument.