Source : Webster's Revised Unabridged Dictionary (1913)

Scientific \Sci`en*tif"ic\, a. [F. scientifique; L. scientia
   science + facere to make.]
   1. Of or pertaining to science; used in science; as,
      scientific principles; scientific apparatus; scientific
      observations.

   2. Agreeing with, or depending on, the rules or principles of
      science; as, a scientific classification; a scientific
      arrangement of fossils.

   3. Having a knowledge of science, or of a science; evincing
      science or systematic knowledge; as, a scientific chemist;
      a scientific reasoner; a scientific argument.

            Bossuet is as scientific in the structure of his
            sentences.                            --Landor.

   {Scientific method}, the method employed in exact science and
      consisting of: (a) Careful and abundant observation and
      experiment. (b) generalization of the results into
      formulated ``Laws'' and statements.

Source : WordNet®

scientific
     adj 1: of or relating to the practice of science; "scientific
            journals"
     2: conforming with the principles or methods used in science;
        "a scientific approach" [ant: {unscientific}]