The Collaborative International Dictionary of English v.0.48:

Self-assertive \Self`-as*sert"ive\, a.
   Disposed to self-assertion; self-asserting.
   [1913 Webster]

WordNet (r) 3.0 (2006):

self-assertive
    adj 1: aggressively self-assured; "an energetic assertive boy
           who was always ready to argue"; "pointing directly at a
           listener is an assertive act" [syn: assertive, self-
           asserting, self-assertive] [ant: unassertive]
    2: offensively self-assertive [syn: bumptious, self-
       assertive]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "self-assertive":
   assertive, audacious, bold, cocksure, controlled, firm-minded,
   forward, impertinent, importunate, independent, intrusive,
   meddlesome, militant, obtrusive, officious, overweening, presuming,
   pushful, pushing, pushy, self-asserting, self-controlled,
   self-expressive, self-possessed, self-restrained, strong-minded,
   strong-willed, sure, uppish, uppity