The Collaborative International Dictionary of English v.0.48:

Perfective \Per*fect"ive\ (p[~e]r*f[e^]k"t[i^]v), a.
   1. Tending or conducing to make perfect, or to bring to
      perfection; -- usually followed by of. "A perfective
      alteration." --Fuller.
      [1913 Webster]

            Actions perfective of their natures.  --Ray.
      [1913 Webster]

   2. (Gram.) Denoting an aspect of verbs which indicates
      completion of an action, and is sometimes explicitly
      marked in verbal inflection, as in the Russian language;
      as, the perfective form of a verb. The use of a perfective
      form rather than the simple past indicates reference to a
      completed event, rather than to a process that took place
      in the past.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

perfective \per*fect"ive\ (p[~e]r*f[e^]k"t[i^]v), n.
   1. (Gram.) The perfective case or aspect.
      [PJC]

   2. (Gram.) A verb in the perfective case or aspect.
      [PJC]

WordNet (r) 3.0 (2006):

perfective
    n 1: a tense of verbs used in describing action that has been
         completed (sometimes regarded as perfective aspect) [syn:
         perfective, perfective tense, perfect, perfect
         tense]
    2: the aspect of a verb that expresses a completed action [syn:
       perfective, perfective aspect]