Which term describes a deviation from the proper or expected course?

The term "aberration" is indeed the correct choice for describing a deviation from the proper or expected course. It often refers to an anomaly or something that is atypical in a given context, suggesting that there has been a departure from what is considered normal or standard. In various fields such as science, psychology, and general usage, the term denotes instances where something strays from the expected path or condition, indicating irregularity or a break from the norm.

In contrast, "abeyance" refers to a state of temporary inactivity or suspension, rather than a deviation from a course. "Abide" means to accept or act in accordance with, and thus does not convey the idea of deviation. "Abhor" means to detest or to have a strong aversion to something, which similarly lacks relevance to the concept of deviation.