What does the term "obscure" mean?

The term "obscure" means something that is not clearly understood or expressed. This can relate to ideas, concepts, or even people that are hidden from view or not widely recognized. When something is described as obscure, it suggests a lack of clarity or visibility, making it difficult for people to comprehend. This aligns perfectly with the answer option that states it is "not clearly understood or expressed."

In contrast, the other choices present meanings that directly oppose the definition of "obscure." Clearly defined and easily understandable refer to clarity and comprehension, which are not characteristics of something that is obscure. Similarly, very popular and well-known describes something that is widely recognized or acknowledged, again contrasting with the notion of obscurity. Understanding the nuance of "obscure" adds depth to the interpretation of various texts and concepts where clarity may be lacking.