Source : Webster's Revised Unabridged Dictionary (1913)

Insensible \In*sen"si*ble\, a. [L. insensibilis: cf. F.
   insensible. See {In-} not, and {Sensible}.]
   1. Destitute of the power of feeling or perceiving; wanting
      bodily sensibility. --Milton.

   2. Not susceptible of emotion or passion; void of feeling;
      apathetic; unconcerned; indifferent; as, insensible to
      danger, fear, love, etc.; -- often used with of or to.

            Accept an obligation without being a slave to the
            giver, or insensible to his kindness. --Sir H.
                                                  Wotton.

            Lost in their loves, insensible of shame. --Dryden.

   3. Incapable of being perceived by the senses; imperceptible.
      Hence: Progressing by imperceptible degrees; slow;
      gradual; as, insensible motion.

            Two small and almost insensible pricks were found
            upon Cleopatra's arm.                 --Sir T.
                                                  Browne.

            They fall away, And languish with insensible decay.
                                                  --Dryden.

   4. Not sensible or reasonable; meaningless. [Obs.]

            If it make the indictment be insensible or
            uncertain, it shall be quashed.       --Sir M. Hale.

   Syn: Imperceptible; imperceivable; dull; stupid; torpid;
        numb; unfeeling; apathetic; stoical; impassive;
        indifferent; unsusceptible; hard; callous.

Source : WordNet®

insensible
     adj 1: incapable of physical sensation; "insensible to pain";
            "insensible earth" [ant: {sensible}]
     2: (followed by `to' or `by') unaware of or indifferent to;
        "insensible to the suffering around him" [syn: {insensible(p)},
         {unaffected(p)}]
     3: barely able to be perceived; "the transition was almost
        indiscernible"; "an almost insensible change" [syn: {indiscernible},
         {undetectable}]
     4: unresponsive to stimulation; "he lay insensible where he had
        fallen"; "drugged and senseless" [syn: {senseless}]