WordNet (r) 3.0 (2006):

thus far
    adv 1: used in negative statement to describe a situation that
           has existed up to this point or up to the present time;
           "So far he hasn't called"; "the sun isn't up yet" [syn:
           so far, thus far, up to now, hitherto,
           heretofore, as yet, yet, til now, until now]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "thus far":
   after a fashion, already, appreciably, as yet, at any rate,
   at best, at least, at most, at the outside, at worst, by this time,
   comparatively, detectably, earlier, fairly, heretofore, hereunto,
   in a manner, in a way, in part, in some measure, incompletely,
   leastwise, merely, mildly, moderately, modestly,
   not comprehensively, not exhaustively, only, part, partially,
   partly, pro tanto, purely, relatively, simply, so far, somewhat,
   still, then as previously, till now, to a degree, to date,
   to some degree, to this day, tolerably, until now, until this time,
   up to now, visibly, yet