What is described as "Any of a class of substances that blunt the senses"?

The description "Any of a class of substances that blunt the senses" refers specifically to narcotics. Narcotics are a type of drug that can dull the body's sensations and can lead to a reduction in pain perception. They achieve this by binding to opioid receptors in the brain and body, resulting in effects such as sedation, pain relief, and a general state of calmness.

Narcotics can cause a sense of detachment or blunting of sensory and emotional experiences, which aligns perfectly with the provided definition. In contrast, stimulants are substances that increase alertness and energy levels; hallucinogens alter perception and can cause hallucinations; and depressants typically slow down the function of the central nervous system but do so differently than narcotics. Thus, the specific characteristics of narcotics make them the answer that best fits the description given.