The Collaborative International Dictionary of English v.0.48:

Insensate \In*sen"sate\, a. [L. insensatus. See In- not, and
   Sensate.]
   Wanting sensibility; destitute of sense; stupid; foolish.
   [1913 Webster]

         The silence and the calm
         Of mute, insensate things.               --Wordsworth.
   [1913 Webster]

         The meddling folly or insensate ambition of statesmen.
                                                  --Buckle.
   -- In*sen"sate*ly, adv. -- In*sen"sate*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

insensate
    adj 1: devoid of feeling and consciousness and animation;
           "insentient (or insensate) stone" [syn: insentient,
           insensate] [ant: animate, sentient]
    2: without compunction or human feeling; "in cold blood"; "cold-
       blooded killing"; "insensate destruction" [syn: cold,
       cold-blooded, inhuman, insensate]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "insensate":
   abiotic, anarchic, anesthetic, angry, asleep, azoic, benumbed,
   bloodless, blustering, blusterous, blustery, brainless, callous,
   chaotic, dead, deadened, dull, dumb, exanimate, fatuous, foolish,
   frantic, frenzied, furious, hard, headless, hellish, ignorant,
   ill-advised, ill-considered, ill-contrived, ill-devised,
   ill-gauged, ill-judged, impassible, imperceptive, impercipient,
   impolitic, impossible, imprudent, inadvisable, inanimate,
   inanimated, inconsiderate, indiscreet, inept, inert, inexpedient,
   infuriate, injudicious, insensible, insensitive, insentient,
   irrational, lackbrained, lean-minded, lean-witted, lifeless, mad,
   mindless, misadvised, misguided, mute, myopic, nitwitted,
   nonconscious, nonliving, not bright, numb, numbed, obdurate,
   obtuse, of little brain, orgasmic, orgastic, pandemoniac,
   pea-brained, pin-brained, raging, ravening, raving, reasonless,
   reckless, rip-roaring, rocky, senseless, shortsighted, silly,
   slackminded, slackwitted, soulless, storming, stormy, tempestuous,
   thick-skinned, thick-witted, thoughtless, troublous, tumultuous,
   turbulent, unadvised, unanimated, unconscious, unconsidered,
   undiscerning, unfeeling, unfelt, unforeseeing, ungifted,
   unintellectual, unintelligent, unperceptive, unreasonable,
   unreasoning, unreflecting, unreflective, unseeing, unsensible,
   unsound, untalented, unthinking, unthoughtful, unwise, uproarious,
   wild, witless