The Collaborative International Dictionary of English v.0.48:

Introspective \In`tro*spec"tive\, a. [Cf. F. introspectif.]
   [1913 Webster]
   1. Inspecting within; seeing inwardly; capable of, or
      exercising, inspection; self-conscious.
      [1913 Webster]

   2. Involving the act or results of conscious knowledge of
      physical phenomena; -- contrasted with associational.
      --J. S. Mill.
      [1913 Webster]

WordNet (r) 3.0 (2006):

introspective
    adj 1: given to examining own sensory and perceptual experiences
           [syn: introspective, introverted, self-examining]
           [ant: extrospective, extroverted]