Which adjective describes something that is tediously repetitious or lacking variety?

The adjective that describes something as tediously repetitious or lacking variety is "monotonous." This term is often used to characterize experiences, tasks, or sounds that are uniform and unchanging, leading to a sense of dullness or boredom. In various contexts, such as music or work routines, a monotonous situation fails to engage the audience or individual due to its repetitive nature, which can be uninspiring or tiresome.

The other choices, while having their own meanings, do not convey the idea of repetitiveness or lack of variety. "Superfluous" refers to something unnecessary or excessive, "marginal" relates to something of minimal significance or importance, and "recluse" describes a person who tends to avoid social interaction or live alone. None of these terms align with the concept of monotony.