The Collaborative International Dictionary of English v.0.48:

Pertinacity \Per`ti*nac"i*ty\, n. [Cf. F. pertinacit['e].]
   The quality or state of being pertinacious; obstinacy;
   perseverance; persistency. --Macaulay.
   [1913 Webster]

   Syn: See Obstinacy.
        [1913 Webster]

WordNet (r) 3.0 (2006):

pertinacity
    n 1: persistent determination [syn: doggedness,
         perseverance, persistence, persistency, tenacity,
         tenaciousness, pertinacity]