Source : Webster's Revised Unabridged Dictionary (1913)

Sinistral \Sin"is*tral\, a.
   1. Of or pertaining to the left, inclining to the left;
      sinistrous; -- opposed to {dextral}.

   2. (Zo["o]l.) Having the whorls of the spire revolving or
      rising to the left; reversed; -- said of certain spiral
      shells.

Source : WordNet®

sinistral
     adj 1: of or on the left; "a sinistral gastropod shell with the
            apex upward has its opening on the left when facing
            the observer"; "a sinistral flatfish lies with the
            left eye uppermost" [ant: {dextral}]
     2: preferring to use left foot or hand or eye; "sinistral
        individuals exhibit dominance of the left hand and eye"