The Collaborative International Dictionary of English v.0.48:

Sopor \So"por\, n. [L.] (Med.)
   Profound sleep from which a person can be roused only with
   difficulty.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sopor
    n 1: a torpid state resembling deep sleep [syn: sleep,
         sopor]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "sopor":
   acedia, aloofness, apathy, ataraxia, ataraxy, benumbedness, blah,
   blahs, catalepsy, coma, comatoseness, detachment, disinterest,
   dispassion, dullness, encephalitis lethargica, heartlessness,
   hebetude, high, hopelessness, inappetence, indifference,
   insouciance, lack of appetite, languidness, lethargicalness,
   lethargy, listlessness, narcohypnosis, narcolepsy, narcoma,
   narcosis, narcotic stupor, narcotization, nod, nonchalance,
   numbness, passiveness, passivity, phlegm, phlegmaticalness,
   phlegmaticness, plucklessness, resignation, resignedness, sedation,
   shock, sleeping sickness, sloth, sluggishness, soporifousness,
   spiritlessness, spunklessness, stupefaction, stupor, supineness,
   swoon, thanatosis, torpidity, torpidness, torpor, trance,
   unconcern, withdrawnness