Source : Webster's Revised Unabridged Dictionary (1913)

Critical \Crit"ic*al\ (kr?t"?-kal), a. [See {Critic}, n.,
   {Crisis}.]
   1. Qualified to criticise, or pass judgment upon, literary or
      artistic productions.

            It is submitted to the judgment of more critical
            ears to direct and determine what is graceful and
            what is not.                          --Holder.

   2. Pertaining to criticism or the critic's art; of the nature
      of a criticism; accurate; as, critical knowledge; a
      critical dissertation.

   3. Inclined to make nice distinctions, or to exercise careful
      judgment and selection; exact; nicely judicious.

            Virgil was so critical in the rites of religion.
            that he would never have brought in such prayers as
            these, if they had not been agreeable to the Roman
            customs.                              --Bp.
                                                  Stillingfleet.

   4. Inclined to criticise or find fault; fastidious; captious;
      censorious; exacting.

            O gentle lady, do not put me to 't, For I am
            nothing, if not critical.             --Shak.

   5. Characterized by thoroughness and a reference to
      principles, as becomes a critic; as, a critical analysis
      of a subject.

   6. [See {Crisis}.] Pertaining to, or indicating, a crisis,
      turning point, or specially important juncture; important
      as regards consequences; hence, of doubtful issue;
      attended with risk; dangerous; as, the critical stage of a
      fever; a critical situation.

            Our circumstances are indeed critical. --Burke.

            The small moment, the exact point, the critical
            minute, on which every good work so much depends.
                                                  --South.

   {Critical angle} (Optics), that angle of incidence of a
      luminous ray at which it is wholly reflected, and no
      portion of it transmitted. The sine of this angle is the
      reciprocal of the refractive index of the medium.

   {Critical philosophy}, the metaphysical system of Kant; -- so
      called from his most important work, the ``Critique of
      Pure Reason.''

   {Critical point} (Physics), a certain temperature, different
      for different gases, but always the same for each gas,
      regarded as the limit above which no amount of pressure
      can produce condensation to a liquid.

Source : WordNet®

critical
     adj 1: marked by a tendency to find and call attention to errors
            and flaws; "a critical attitude" [ant: {uncritical}]
     2: at or of a point at which a property or phenomenon suffers
        an abrupt change especially having enough mass to sustain
        a chain reaction; "a critical temperature of water is 100
        degrees C--its boiling point at standard atmospheric
        pressure"; "critical mass"; "go critical" [ant: {noncritical}]
     3: characterized by careful evaluation and judgment; "a
        critical reading"; "a critical dissertation"; "a critical
        analysis of Melville's writings" [ant: {uncritical}]
     4: urgently needed; absolutely necessary; "a critical element
        of the plan"; "critical medical supplies"; "vital for a
        healthy society"; "of vital interest" [syn: {vital}]
     5: forming or having the nature of a turning point or crisis;
        "a critical point in the campaign"; "the critical test"
        [syn: {decisive}]
     6: being in or verging on a state of crisis or emergency; "a
        critical shortage of food"; "a critical illness"; "an
        illness at the critical stage" [ant: {noncritical}]
     7: of or involving or characteristic of critics or criticism;
        "critical acclaim"