The Collaborative International Dictionary of English v.0.48:

Conscious \Con"scious\, a. [L. conscius; con- + scire to know.
   See Conscience.]
   1. Possessing the faculty of knowing one's own thoughts or
      mental operations.
      [1913 Webster]

            Some are thinking or conscious beings, or have a
            power of thought.                     --I. Watts.
      [1913 Webster]

   2. Possessing knowledge, whether by internal, conscious
      experience or by external observation; cognizant; aware;
      sensible.
      [1913 Webster]

            Her conscious heart imputed suspicion where none
            could have been felt.                 --Hawthorne.
      [1913 Webster]

            The man who breathes most healthilly is least
            conscious of his own breathing.       --De Quincey.
      [1913 Webster]

   3. Made the object of consciousness; known to one's self; as,
      conscious guilt.
      [1913 Webster]

            With conscious terrors vex me round.  --Milton.

   Syn: Aware; apprised; sensible; felt; known.
        [1913 Webster]

WordNet (r) 3.0 (2006):

conscious
    adj 1: intentionally conceived; "a conscious effort to speak
           more slowly"; "a conscious policy" [syn: conscious,
           witting]
    2: knowing and perceiving; having awareness of surroundings and
       sensations and thoughts; "remained conscious during the
       operation"; "conscious of his faults"; "became conscious that
       he was being followed" [ant: unconscious]
    3: (followed by `of') showing realization or recognition of
       something; "few voters seem conscious of the issue's
       importance"; "conscious of having succeeded"; "the careful
       tread of one conscious of his alcoholic load"- Thomas Hardy

Moby Thesaurus II by Grady Ward, 1.0:

137 Moby Thesaurus words for "conscious":
   aboveground, advertent, advised, agog, aimed, aimed at, alert,
   alive, alive and kicking, alive to, all ears, all eyes,
   all-knowing, among the living, animate, animated, apperceptive,
   appercipient, apprehending, apprehensive, assiduous, attentive,
   au courant, awake, aware, bashful, breathing, calculated,
   capable of life, careful, cognizant, comprehending, concentrated,
   confused, considered, contemplated, conversant, coy, deliberate,
   deliberated, demure, designed, diligent, earnest,
   endowed with life, enlivened, envisaged, envisioned, existent,
   finical, finicking, finicky, heedful, impressible, impressionable,
   impressive, in the flesh, inarticulate, insightful, inspirited,
   instinct with life, intelligent, intended, intense, intent,
   intentional, intentive, knowing, knowledgeable, live, living,
   long-lived, mannered, meant, meditated, meticulous, mindful, mousy,
   nice, niggling, noticing, observant, observing, of design,
   omniscient, on the ball, on the job, open-eared, open-eyed,
   openmouthed, perceiving, perceptive, percipient, perspicacious,
   planned, prehensile, projected, proposed, purposed, purposeful,
   purposive, quick, receptive, regardful, sagacious, self-conscious,
   sensible, sensile, sensitive to, sentient, shamefaced, shamefast,
   shrewd, shy, skittish, stammering, studied, susceptible,
   susceptive, teleological, tenacious of life, timid, timorous,
   understanding, up, very much alive, viable, vigilant, vital,
   vivified, voluntary, watchful, wide-awake, willful, wise, witting,
   zoetic