Source : Webster's Revised Unabridged Dictionary (1913)

Impassive \Im*pas"sive\, a.
   Not susceptible of pain or suffering; apathetic; impassible;
   unmoved.

         Impassive as the marble in the quarry.   --De Quincey.

         On the impassive ice the lightings play. --Pope.
   -- {Im*pas"sive*ly}, adv. -- {Im*pas"sive*ness}, n.

Source : WordNet®

impassive
     adj 1: having or revealing little emotion or sensibility; not
            easily aroused or excited; "her impassive remoteness";
            "he remained impassive, showing neither interest in
            nor concern for our plight"- Nordhoff & Hall; "a
            silent stolid creature who took it all as a matter of
            course"-Virginia Woolf; "her face showed nothing but
            stolid indifference" [syn: {stolid}]
     2: deliberately impassive in manner; "deadpan humor"; "his face
        remained expressionless as the verdict was read" [syn: {deadpan},
         {expressionless}, {poker-faced}, {unexpressive}]