Which of the following best defines 'obscure'?

The term 'obscure' is best defined as uncertain or not known. This definition captures the essence of what it means when something is described as obscure—it indicates a lack of clarity or understanding, often suggesting that the information is hidden or not easily accessible. In various contexts, whether in literature, communication, or knowledge, when something is obscure, it requires further investigation or explanation to gain clarity.

The other definitions provided do not align with this meaning. Describing something as well-known and famous conveys the opposite sentiment, indicating that it is clear and easily recognizable, while discovered and clear implies accessibility and understanding, again contradicting the notion of obscurity. Similarly, commonly understood reflects a widely shared knowledge or clarity, which does not encapsulate the uncertainty associated with obscurity.