Which of the following describes eating or drinking in moderation?

The term that best describes eating or drinking in moderation is "abstemious." This word refers to the practice of restraining oneself from indulging excessively, particularly when it comes to food and drink. Individuals who are abstemious exercise self-control and maintain a balanced approach to consumption, which aligns perfectly with the concept of moderation.

In contrast, the other options do not convey this meaning. "Abash" means to make someone feel embarrassed or ashamed, which is unrelated to the concept of moderation. "Abhor" refers to a strong dislike or hatred of something, and does not pertain to consumption behavior. "Aegis" denotes protection or support, often used in a different context such as legal or organizational protection, and is also not relevant to the idea of moderation in eating or drinking. Thus, "abstemious" stands out as the appropriate choice for describing moderation in eating and drinking.