Which term refers to something mysterious or puzzling?

The term "enigmatic" specifically refers to something that is mysterious, puzzling, or difficult to understand. It captures the essence of something that provokes curiosity and intrigue because it is not easily deciphered. In various contexts, whether in literature, art, or everyday situations, something described as enigmatic often leaves observers with questions or a sense of wonder, as its meaning or significance remains elusive.

In contrast, the other choices do not carry the same connotation of mystery. The term "opaque" typically refers to something that is not able to be seen through or understood clearly, while "ambiguous" denotes something that can be interpreted in multiple ways and lacks clarity. "Transparent," on the other hand, implies clarity and openness, making information easy to understand. Thus, "enigmatic" stands out as the most suitable choice to convey the sense of mystery and puzzleness that the question describes.