The Collaborative International Dictionary of English v.0.48:

Hasheesh \Hash"eesh\ Hashish \Hash"ish\ (h[a^]sh"[=e]sh), n.
   [Ar. hash[imac]sh.]
   A slightly acrid gum resin produced by the common hemp
   (Cannabis sativa), of the variety Indica, when cultivated
   in a warm climate; also, the tops of the plant, from which
   the resinous product is obtained. It is narcotic, and has
   long been used in the East for its intoxicating effect. The
   active psychoactive principle has been identified as
   tetrahydrocannabinol. See Bhang, and Ganja.

   Syn: hash.
        [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

hashish
    n 1: purified resinous extract of the hemp plant; used as a
         hallucinogen [syn: hashish, hasheesh, haschisch,
         hash]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "hashish":
   DET, DMT, LSD, Mary Jane, STP, THC, acid, antidepressant,
   ataractic, diethyltryptamine, dimethyltryptamine, gage, ganja,
   grass, hallucinogen, hash, hay, hemp, joint, kava, marijuana,
   mescal, mescal bean, mescal button, mescaline, mind-altering drug,
   mind-blowing drug, mind-expanding drug, morning glory seeds,
   peyote, pot, psilocin, psilocybin, psychedelic, psychic energizer,
   psychoactive drug, psychochemical, psychotomimetic, reefer, roach,
   stick, tea, tranquilizer, weed