The Collaborative International Dictionary of English v.0.48:

Pertinacious \Per`ti*na"cious\, a. [L. pertinax, -acis; per +
   tenax tenacious. See Per-, and Tenacious.]
   1. Holding or adhering to any opinion, purpose, or design,
      with obstinacy; perversely persistent; obstinate; as,
      pertinacious plotters; a pertinacious beggar.
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   2. Resolute; persevering; constant; steady.
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            Diligence is a steady, constant, and pertinacious
            study.                                --South.
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   Syn: Obstinate; stubborn; inflexible; unyielding; resolute;
        determined; firm; constant; steady.
        [1913 Webster] -- Per`ti*na"cious*ly, adv. --
        Per`ti*na"cious*ness, n.
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