The Collaborative International Dictionary of English v.0.48:

Especially \Es*pe"cial*ly\, adv.
   In an especial manner; chiefly; particularly; peculiarly; in
   an uncommon degree.
   [1913 Webster]

WordNet (r) 3.0 (2006):

especially
    adv 1: to a distinctly greater extent or degree than is common;
           "he was particularly fussy about spelling"; "a
           particularly gruesome attack"; "under peculiarly tragic
           circumstances"; "an especially (or specially) cautious
           approach to the danger" [syn: particularly,
           peculiarly, especially, specially]
    2: in a special manner; "a specially arranged dinner" [syn:
       specially, especially]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "especially":
   a fortiori, above all, all the more, chiefly, concretely,
   conspicuously, definitely, distinctively, distinctly, dominantly,
   eminently, even, ever so, exactly, exceptionally, expressly,
   extraordinarily, first, first of all, firstly, in chief, in detail,
   in particular, in the main, indeed, item by item, mainly, markedly,
   minutely, more than ever, mostly, never so, no end, notably,
   noticeably, outstandingly, particularly, peculiarly, precisely,
   predominantly, preeminently, primarily, principally, remarkably,
   separately, signally, singly, singularly, special, specially,
   specifically, still more, strikingly, supremely, to be specific,
   uncommonly, uniquely, unusually, yea