The Collaborative International Dictionary of English v.0.48:

Significant \Sig*nif"i*cant\, a. [L. significans, -antis, p. pr.
   of significare. See Signify.]
   1. Fitted or designed to signify or make known something
      having a meaning; standing as a sign or token; expressive
      or suggestive; as, a significant word or sound; a
      significant look.
      [1913 Webster]

            It was well said of Plotinus, that the stars were
            significant, but not efficient.       --Sir W.
                                                  Raleigh.
      [1913 Webster]

   2. Deserving to be considered; important; momentous; as, a
      significant event.
      [1913 Webster]

   Significant figures (Arith.), the figures which remain to
      any number, or decimal fraction, after the ciphers at the
      right or left are canceled. Thus, the significant figures
      of 25,000, or of .0025, are 25.
      [1913 Webster]