The Collaborative International Dictionary of English v.0.48:

Furthermore \Fur"ther*more"\, adv.
   or conj. Moreover; besides; in addition to what has been
   said.
   [1913 Webster]

WordNet (r) 3.0 (2006):

furthermore
    adv 1: in addition; "computer chess games are getting cheaper
           all the time; furthermore, their quality is improving";
           "the cellar was dark; moreover, mice nested there"; "what
           is more, there's no sign of a change" [syn:
           furthermore, moreover, what is more]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "furthermore":
   above, additionally, again, all included, along, also, altogether,
   among other things, and all, and also, and so, as well, au reste,
   beside, besides, beyond, else, en plus, extra, farther,
   for lagniappe, further, in addition, inter alia, into the bargain,
   item, likewise, more, moreover, on the side, on top of, over, plus,
   similarly, then, therewith, to boot, too, yea, yet