What term describes something that is not clearly or sharply delineated?

The term that describes something that is not clearly or sharply delineated is "indistinct." This word conveys the idea of lacking clarity or definition, making it difficult to perceive or recognize. When something is described as indistinct, it suggests that it does not have sharp boundaries or precise outlines, which can lead to uncertainty in understanding or identifying what it is.

In contrast, while "vague," "obscure," and "ambiguous" also pertain to lack of clarity in different ways, they each carry unique nuances. For instance, "vague" usually refers to statements or ideas that are not expressed clearly, while "obscure" can imply that something is hidden or not easily understood due to a lack of prominence. "Ambiguous" suggests multiple possible interpretations or meanings, leading to confusion. However, "indistinct" specifically aligns with the notion of something being imprecise in its physical or conceptual boundaries, which makes it the most appropriate term in this context.