The Collaborative International Dictionary of English v.0.48:

Excruciate \Ex*cru"ci*ate\, v. t. [imp. & p. p. Excruciated;
   p. pr. & vb. n. Excruciating.]
   To inflict agonizing pain upon; to torture; to torment
   greatly; to rack; as, to excruciate the heart or the body.
   [1913 Webster]

         Their thoughts, like devils, them excruciate.
                                                  --Drayton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Excruciating \Ex*cru"ci*a`ting\
   Torturing; racking. "Excruciating pain." --V. Knox.
   "Excruciating fears." --Bentley -- Ex*cru"ci*a`ting*ly,
   adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

excruciating
    adj 1: extremely painful [syn: agonizing, agonising,
           excruciating, harrowing, torturing, torturous,
           torturesome]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "excruciating":
   acute, afflictive, agonizing, atrocious, biting, consuming,
   cramping, cruel, desolating, distressful, distressing, exquisite,
   extreme, gnawing, grave, griping, hard, harrowing, harsh,
   heartbreaking, heartrending, heartsickening, heartwounding,
   hurtful, hurting, insufferable, intense, keen, painful, paroxysmal,
   piercing, poignant, pungent, racking, rending, severe, sharp,
   shooting, spasmatic, spasmic, spasmodic, stabbing, stinging,
   tearing, tormenting, torturing, torturous, unbearable, unendurable,
   vivid