What is Narcotic?

Legal Definition
The term narcotic (/nɑːrˈkɒtk/, from ancient Greek ναρκῶ narkō, "to make numb") originally referred medically to any psychoactive compound with sleep-inducing properties. In the United States, it has since become associated with opiates and opioids, commonly morphine and heroin, as well as derivatives of many of the compounds found within raw opium latex. The primary three are morphine, codeine, and thebaine (while thebaine itself is only very mildly psychoactive, it is a crucial precursor in the vast majority of semi-synthetic opioids, such as hydrocodone). Legally speaking, the term "narcotic" is imprecisely defined and typically has negative connotations. When used in a legal context in the U.S., a narcotic drug is simply one that is totally prohibited, or one that is used in violation of governmental regulation, such as heroin or cannabis.

In the medical community, the term is more precisely defined and generally does not carry the same negative connotations.

Statutory classification of a drug as a narcotic often increases the penalties for violation of drug control statutes. For example, although federal law classifies both cocaine and amphetamines as "Schedule II" drugs, the penalty for possession of cocaine is greater than the penalty for possession of amphetamines because cocaine, unlike amphetamines, is classified as a narcotic.
-- Wikipedia
Legal Definition
term given to a group of drugs that includes morphine and heroin that reduce pain and produce sleep or stupor.
Legal Definition
Trichloromethane (CHCl3) or chloroform is an example of a substance that causes narcosis.