Various definitions exist when describing the term opiate but they all pretty much describe the same thing. Some of the common definitions for an opiate include:
a) A drug containing or derived from opium and tending to induce sleep and alleviate pain
b) Something that induces rest or inaction or quiets uneasiness
c) A medication or an illegal drug that is derived from the opium poppy or that mimics the effect of an opiate (a synthetic opiate). Opiate drugs are narcotic sedatives that depress activity of the central nervous system, reduce pain, and induce sleep. Side effects may include oversedation, nausea, and constipation. Long-term use of opiates can produce addiction and overuse can cause overdose and potentially death.
d) Something that dulls the senses and induces relaxation or torpor.
e) Any of various drugs such as morphine or heroin that act on opioid receptors
f) A drug, hormone, or other chemical substance having sedative or narcotic effects similar to those containing opium or its derivatives.