The Collaborative International Dictionary of English v.0.48:

Sinistrous \Sin"is*trous\, a. [See Sinister.]
   1. Being on the left side; inclined to the left; sinistral.
      "Sinistrous gravity." --Sir T. Browne.
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   2. Wrong; absurd; perverse.
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            A knave or fool can do no harm, even by the most
            sinistrous and absurd choice.         --Bentley.
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