The Collaborative International Dictionary of English v.0.48:

Partly \Part"ly\, adv.
   In part; in some measure of degree; not wholly. "I partly
   believe it." --1 Cor. xi. 18.
   [1913 Webster]

WordNet (r) 3.0 (2006):

partly
    adv 1: in part; in some degree; not wholly; "I felt partly to
           blame"; "He was partially paralyzed" [syn: partially,
           partly, part] [ant: all, altogether,
           completely, entirely, totally, whole, wholly]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "partly":
   after a fashion, appreciably, at any rate, at best, at least,
   at most, at the least, at the most, at the outside, at worst,
   comparatively, detectably, fairly, half, halfway, in a manner,
   in a way, in part, in some measure, incompletely, leastwise,
   merely, mildly, moderately, modestly, not comprehensively,
   not exhaustively, one-and-a-half, only, part, partial, partially,
   pro tanto, purely, relatively, simply, so far, somewhat, thus far,
   to a degree, to some degree, tolerably, visibly