The Collaborative International Dictionary of English v.0.48:

Largely \Large"ly\, adv.
   In a large manner. --Dryden. --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

largely
    adv 1: in large part; mainly or chiefly; "These accounts are
           largely inactive" [syn: largely, mostly, for the
           most part]
    2: on a large scale; "the sketch was so largely drawn that you
       could see it from the back row"

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "largely":
   a deal, a great deal, a lot, abundantly, altogether, as a rule,
   as all creation, as all get-out, at bottom, basically, beaucoup,
   by and large, chiefly, completely, comprehensively, considerable,
   considerably, entirely, essentially, ever so, ever so much,
   exhaustively, fully, fundamentally, galore, generally, globally,
   greatly, highly, hundred per cent, in full, in full measure,
   in general, in great measure, in the main, inclusively, inside out,
   integrally, mainly, mostly, much, muchly, never so, no end,
   no end of, not a little, on the whole, one and all, outright,
   overall, plenty, predominantly, pretty much, primarily,
   principally, roundly, so, so very much, thoroughly, to the hilt,
   to the skies, totally, tout a fait, unconditionally, unreservedly,
   very much, wholly