The Collaborative International Dictionary of English v.0.48:

Critical \Crit"ic*al\ (kr[i^]t"[i^]*kal), a. [See Critic, n.,
   Crisis.]
   [1913 Webster]
   1. Qualified to criticise, or pass judgment upon, literary or
      artistic productions.
      [1913 Webster]

            It is submitted to the judgment of more critical
            ears to direct and determine what is graceful and
            what is not.                          --Holder.
      [1913 Webster]

   2. Pertaining to criticism or the critic's art; of the nature
      of a criticism; accurate; as, critical knowledge; a
      critical dissertation.
      [1913 Webster]

   3. Inclined to make nice distinctions, or to exercise careful
      judgment and selection; exact; nicely judicious.
      [1913 Webster]

            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.
      [1913 Webster]

   4. Inclined to criticise or find fault; fastidious; captious;
      censorious; exacting.
      [1913 Webster]

            O gentle lady, do not put me to 't,
            For I am nothing, if not critical.    --Shak.
      [1913 Webster]

   5. Characterized by thoroughness and a reference to
      principles, as becomes a critic; as, a critical analysis
      of a subject.
      [1913 Webster]

   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.
      [1913 Webster]

            Our circumstances are indeed critical. --Burke.
      [1913 Webster]

            The small moment, the exact point, the critical
            minute, on which every good work so much depends.
                                                  --South.
      [1913 Webster]

   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."
      [1913 Webster]