The Collaborative International Dictionary of English v.0.48:

Primarily \Pri"ma*ri*ly\, adv.
   In a primary manner; in the first place; in the first place;
   in the first intention; originally.
   [1913 Webster]

WordNet (r) 3.0 (2006):

primarily
    adv 1: for the most part; "he is mainly interested in
           butterflies" [syn: chiefly, principally, primarily,
           mainly, in the main]
    2: of primary import; "this is primarily a question of
       economics"; "it was in the first place a local matter" [syn:
       primarily, in the first place] [ant: secondarily]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "primarily":
   a fortiori, ab initio, ab ovo, aborigine, above all, all the more,
   at bottom, at first, at heart, at the core, at the start, au fond,
   basically, before everything, chiefly, dominantly, especially,
   essentially, even, ever so, first, first and foremost,
   first of all, first thing, firstly, from the beginning,
   fundamentally, generally, in chief, in essence, in itself,
   in substance, in the beginning, in the main, indeed, initially,
   largely, mainly, materially, more than ever, mostly, never so,
   no end, on the whole, originally, overall, particularly,
   peculiarly, per se, predominantly, primitively, primo, principally,
   still more, substantially, yea