What term describes a state of being sleepy or drowsy?

The term that describes a state of being sleepy or drowsy is "somnolent." This word originates from the Latin term "somnolentus," which is related to sleep. When someone is described as somnolent, it implies that they are experiencing a strong inclination to sleep, or they appear drowsy and lethargic. This can be the result of various factors, including lack of sleep, certain medications, or health conditions.

In contrast, the other options do not convey the same meaning. "Sonorous" refers to a sound that is deep, full, and rich, often describing vocal quality. "Stanch" is related to stopping the flow of something, usually in reference to blood or a liquid. "Surreptitious," on the other hand, denotes something that is done secretly or stealthily, often to avoid notice. Thus, "somnolent" is the precise term for expressing a state of sleepiness or drowsiness.