Which term is used to describe when sleep is interrupted and irregular?

The term "fitful" is specifically used to describe sleep that is characterized by interruptions and irregular patterns. It evokes the idea of something that occurs in a sporadic and inconsistent manner, often indicating that the sleep is not deep or restful. This term paints a picture of a restless night where one might wake frequently or have difficulty staying asleep, leading to a feeling of fatigue upon waking.

In contrast, the other options do not relate to sleep patterns. "Fastidious" describes someone who is very attentive to detail and hard to please, while "revelry" signifies lively and noisy festivities or celebrations, which is not connected to the state of sleep. "Prostrate" refers to lying flat or being overwhelmed or incapacitated, which, while it could relate to fatigue, does not specifically describe the nature of sleep interruption. Therefore, "fitful" is the most accurate descriptor for irregular and interrupted sleep.