The Collaborative International Dictionary of English v.0.48:

Persist \Per*sist"\, v. i. [imp. & p. p. Persisted; p. pr. &
   vb. n. Persisting.] [L. persistere; per + sistere to stand
   or be fixed, fr. stare to stand: cf. F. persister. See
   Per-, and Stand.]
   To stand firm; to be fixed and unmoved; to stay; to continue
   steadfastly; especially, to continue fixed in a course of
   conduct against opposing motives; to persevere; -- sometimes
   conveying an unfavorable notion, as of doggedness or
   obstinacy.
   [1913 Webster]

         If they persist in pointing their batteries against
         particular persons, no laws of war forbid the making
         reprisals.                               --Addison.
   [1913 Webster]

         Some positive, persisting fops we know,
         Who, if once wrong, will needs be always so. --Pope.
   [1913 Webster]

         That face persists.
         It floats up; it turns over in my mind.  --Mrs.
                                                  Browning.
   [1913 Webster]

   Syn: See Persevere, and Insist.
        [1913 Webster] Persistence

The Collaborative International Dictionary of English v.0.48:

Persisting \Per*sist"ing\, a.
   Inclined to persist; tenacious of purpose; persistent. --
   Per*sist"ing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

persisting
    adj 1: relentless and indefatigable in pursuit or as if in
           pursuit; "impossible to escape the dogging fears" [syn:
           dogging, persisting]