The Collaborative International Dictionary of English v.0.48:

Consciousness \Con"scious*ness\, n.
   1. The state of being conscious; knowledge of one's own
      existence, condition, sensations, mental operations, acts,
      etc.
      [1913 Webster]

            Consciousness is thus, on the one hand, the
            recognition by the mind or "ego" of its acts and
            affections; -- in other words, the self-affirmation
            that certain modifications are known by me, and that
            these modifications are mine.         --Sir W.
                                                  Hamilton.
      [1913 Webster]

   2. Immediate knowledge or perception of the presence of any
      object, state, or sensation. See the Note under
      Attention.
      [1913 Webster]

            Annihilate the consciousness of the object, you
            annihilate the consciousness of the operation. --Sir
                                                  W. Hamilton.
      [1913 Webster]

            And, when the steam
            Which overflowed the soul had passed away,
            A consciousness remained that it had left.
            . . . images and precious thoughts
            That shall not die, and can not be destroyed.
                                                  --Wordsworth.
      [1913 Webster]

            The consciousness of wrong brought with it the
            consciousness of weakness.            --Froude.
      [1913 Webster]

   3. Feeling, persuasion, or expectation; esp., inward sense of
      guilt or innocence. [R.]
      [1913 Webster]

            An honest mind is not in the power of a dishonest:
            to break its peace there must be some guilt or
            consciousness.                        --Pope.
      [1913 Webster]

WordNet (r) 3.0 (2006):

consciousness
    n 1: an alert cognitive state in which you are aware of yourself
         and your situation; "he lost consciousness" [ant:
         unconsciousness]
    2: having knowledge of; "he had no awareness of his mistakes";
       "his sudden consciousness of the problem he faced"; "their
       intelligence and general knowingness was impressive" [syn:
       awareness, consciousness, cognizance, cognisance,
       knowingness] [ant: incognizance]

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "consciousness":
   advertence, advertency, alertness, all-night vigil, apperception,
   appreciation, appreciativeness, assiduity, assiduousness,
   attention, attention span, attentiveness, awareness, brain, care,
   carefulness, cognition, cognizance, concentration, concern,
   consideration, diligence, ear, earnestness, experience, faculties,
   feeling, head, heed, heedfulness, insight, insomnia, insomniac,
   insomnolence, insomnolency, intellect, intellectual gifts,
   intellectuals, intelligence, intentiveness, intentness,
   lidless vigil, mentality, mindfulness, noesis, note, notice,
   observance, observation, parts, percept, perception, realization,
   recognition, regard, regardfulness, remark, respect, response,
   response to stimuli, restlessness, sensation, sense,
   sense impression, sense perception, senses, sensibility,
   sensory experience, sentience, sleeplessness, thought,
   tossing and turning, vigil, wake, wakefulness, wise man, wits