Which term best describes something that is not appropriate or suitable?

The term "inappropriate" specifically indicates something that is not suitable or fitting for a particular situation or context. It directly conveys the idea of something being out of place, offensive, or not adhering to social norms, expectations, or standards. This word is commonly used to describe behavior, language, or actions that do not align with what is considered acceptable or proper in a given circumstance.

In contrast, the other terms convey a different meaning. "Acceptable" implies that something meets standards and is suitable, while "relevant" pertains to something that is directly connected or applicable to the matter at hand. "Fitting" suggests that something is appropriate and suitable, often enhancing the context in which it is placed. Therefore, "inappropriate" stands out as the best descriptor for something that fails to meet the required standards of suitability.