WordNet (r) 3.0 (2006):

kind of
    adv 1: to some (great or small) extent; "it was rather cold";
           "the party was rather nice"; "the knife is rather dull";
           "I rather regret that I cannot attend"; "He's rather good
           at playing the cello"; "he is kind of shy" [syn:
           rather, kind of, kinda, sort of]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "kind of":
   a bit, a little, as it were, extremely, fairly, in a manner,
   in a measure, in a way, in some measure, moderately, more, pretty,
   quite, rather, scarcely, slightly, so to speak, somewhat, sort of,
   to a degree, to some extent, very