an addictive drug derived from consisting of the dried juice of the unripe seed capsules of the opium poppy seeds, containing morphine and other narcotic alkaloids
Thou hast the keys of Paradise, oh just, subtle, and mighty opium — De Quincey
something that has an addictive effect, esp something that inhibits thought or action
Has anything replaced religion as the opium of the people?
[Middle English via Latin from Greek opion poppy juice, dimin. of opos sap]