Source : Webster's Revised Unabridged Dictionary (1913)

Passionless \Pas"sion*less\, a.
   Void of passion; without anger or emotion; not easily
   excited; calm. ``Self-contained and passionless.''
   --Tennyson.

Source : WordNet®

passionless
     adj 1: not passionate; "passionless observation of human nature"
            [ant: {passionate}]
     2: unmoved by feeling; "he kept his emotionless objectivity and
        faith in the cause he served"; "this passionless girl was
        like an icicle in the sunshine"-Margaret Deland [syn: {emotionless}]