Soporific
Part of speech: noun
Definition: Something inducing sleep, especially a drug
Part of speech: adjective
Definition: Tending to induce sleep.
Narcotic
Part of speech: noun
Definition: Any class of substances or drugs, that reduces pain, induces sleep and may alter mood or behaviour.Any type of numbing drug.Certain illegal drugs.
Part of speech: adjective
Definition: Of, or relating to narcotics.Inducing sleep; causing narcosis.
Example sentence: Why are online games so addictive? It's mostly the narcotic appeal of 'leveling.'