a drug that produces numbness or stupor; often taken for pleasure or to reduce pain; extensive use can lead to addiction
"After taking too much of the prescribed narcotic, he stumbled out of bed and forgot why he had been in his room."
Any substance or drug that reduces pain, induces sleep and may alter mood or behaviour; in some contexts, especially in reference to the opiates-and-opioids class, especially in reference to illegal drugs, and often both.
"The doctor prescribed a strong narcotic for his back surgery because he was in too much pain to function without it."
Of, or relating to narcotics.
"The prison doctor specializes in treating patients who have developed a severe addiction to narcotic painkillers after years of chronic back pain."