The Collaborative International Dictionary of English v.0.48:

Rarely \Rare"ly\ (r[^a]r"l[y^]), adv.
   1. In a rare manner or degree; seldom; not often; as, things
      rarely seen.
      [1913 Webster]

   2. Finely; excellently; with rare skill. See 3d Rare, 2.
      [1913 Webster]

            The person who played so rarely on the flageolet.
                                                  --Sir W.
                                                  Scott.
      [1913 Webster]

            The rest of the apartments are rarely gilded.
                                                  --Evelyn.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rarely
    adv 1: not often; "we rarely met" [syn: rarely, seldom]
           [ant: frequently, oft, often, oftentimes,
           ofttimes]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "rarely":
   abnormally, at infrequent intervals, exiguously, extremely, hardly,
   hardly ever, here and there, in places, in spots, incredibly,
   infrequently, little, meagerly, not often, piddlingly, scantily,
   scarcely, scarcely ever, scrimpily, seldom, seldom if ever,
   skimpily, sparsely, sparsim, spottily, stingily, uncommon,
   uncommonly, uncustomarily, unexpectedly, unfrequently, unnaturally,
   unoften, unordinarily, unusually, very seldom