The Collaborative International Dictionary of English v.0.48:

Opiate \O"pi*ate\, n. [From Opium: cf. F. opiat.]
   1. Originally, a medicine of a thicker consistency than
      sirup, prepared with opium. --Parr.
      [1913 Webster]

   2. Any medicine that contains opium, and has the quality of
      inducing sleep or repose; a narcotic.
      [1913 Webster]

   3. Anything which induces rest or inaction; that which quiets
      uneasiness.
      [1913 Webster]

            They chose atheism as an opiate.      --Bentley.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Opiate \O"pi*ate\, a. [See Opium.]
   Inducing sleep; somniferous; narcotic; hence, anodyne;
   causing rest, dullness, or inaction; as, the opiate rod of
   Hermes. --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Opiate \O"pi*ate\, v. t.
   To subject to the influence of an opiate; to put to sleep.
   [R.] --Fenton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

opiate
    n 1: a narcotic drug that contains opium or an opium derivative

Moby Thesaurus II by Grady Ward, 1.0:

106 Moby Thesaurus words for "opiate":
   Amytal, Amytal pill, Demerol, Dolophine, H, Luminal, Luminal pill,
   M, Mickey Finn, Nembutal, Nembutal pill, Seconal, Seconal pill,
   Tuinal, Tuinal pill, accept, alcohol, amobarbital sodium,
   analgesic, anesthetic, anodyne, barb, barbiturate,
   barbiturate pill, believe, black stuff, blue, blue angel,
   blue devil, blue heaven, blue velvet, calmative, chloral hydrate,
   codeine, codeine cough syrup, consider, depressant, depressor,
   dolly, dope, downer, drug, goofball, hard stuff, heroin, hold, hop,
   horse, hypnotic, judge, junk, knockout drop, knockout drops,
   laudanum, liquor, lotus, lullaby, mandrake, meperidine, methadone,
   morphia, morphine, narcotic, nightcap, opinion, opium, pacifier,
   pain killer, pain-killer, paregoric, pen yan, phenobarbital,
   phenobarbital sodium, poppy, purple heart, quietener, rainbow, red,
   regard, scag, secobarbital sodium, sedative, shit, sleep-bringer,
   sleep-inducer, sleep-producer, sleeper, sleeping draught,
   sleeping pill, sleepy, smack, sodium thiopental, somnifacient,
   somniferous, soother, soothing syrup, soporific, speculate, tar,
   think, tranquilizer, turps, view, white stuff, yellow,
   yellow jacket



The Devil's Dictionary (1881-1906):

OPIATE, n.  An unlocked door in the prison of Identity.  It leads into
the jail yard.