What describes the quality of having a strong taste or smell that is sharp and unpleasant?

The quality described in the question refers to a strong taste or smell that is sharp and unpleasant, which is aptly captured by the word "acrid." This term is commonly used to characterize sensations that are intensely irritating or bitter. For example, the smell of burning rubber or the taste of strong vinegar would be described as acrid.

The other options do not convey this specific meaning. "Copious" refers to something abundant or plentiful, often used in context with large quantities. "Azure" pertains to a bright blue color and is not related to taste or smell at all. "Fitful" describes something that is irregular or intermittent, often used in reference to sleep or activity, but it does not relate to the quality of taste or smell. Hence, "acrid" is the only term that directly addresses the nature of a strong, sharp, and unpleasant taste or smell.