The Collaborative International Dictionary of English v.0.48:

Easily \Eas"i*ly\, adv. [From Easy.]
   1. With ease; without difficulty or much effort; as, this
      task may be easily performed; that event might have been
      easily foreseen.
      [1913 Webster]

   2. Without pain, anxiety, or disturbance; as, to pass life
      well and easily. --Sir W. Temple.
      [1913 Webster]

   3. Readily; without reluctance; willingly.
      [1913 Webster]

            Not soon provoked, she easily forgives. --Prior.
      [1913 Webster]

   4. Smoothly; quietly; gently; gracefully; without ?umult or
      discord.
      [1913 Webster]

   5. Without shaking or jolting; commodiously; as, a carriage
      moves easily.
      [1913 Webster]

WordNet (r) 3.0 (2006):

easily
    adv 1: with ease (`easy' is sometimes used informally for
           `easily'); "she was easily excited"; "was easily
           confused"; "he won easily"; "this china breaks very
           easily"; "success came too easy" [syn: easily, easy]
    2: without question; "easily the best book she's written"
    3: indicating high probability; in all likelihood; "I might well
       do it"; "a mistake that could easily have ended in disaster";
       "you may well need your umbrella"; "he could equally well be
       trying to deceive us" [syn: well, easily]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "easily":
   absolutely, actually, assuredly, by far, cautiously, certainly,
   circumspectly, clearly, comfortably, commodiously, competently,
   compliantly, conclusively, conveniently, cozily, crawlingly,
   creepingly, decidedly, definitely, definitively, deliberately,
   delicately, dexterously, dilatorily, doubtless, doubtlessly,
   easy as pie, efficiently, effortlessly, facilely, falteringly,
   far and away, fluently, freely, gently, haltingly, handily,
   hands down, idly, in low gear, in march time, in slow motion,
   in slow tempo, indeed, indisputably, indolently, indubitably,
   languidly, languorously, leisurely, lightly, like clockwork,
   like nothing, limpingly, lingeringly, loiteringly, luxuriously,
   moderately, most likely, no doubt, no sweat, obviously,
   on easy terms, patently, peacefully, pokily, pokingly, positively,
   probably, readily, really, relaxedly, reluctantly, reposefully,
   restfully, roomily, simply, slow, slowly, sluggishly, smoothly,
   snugly, softly, submissively, surely, swimmingly, tarryingly,
   tenderly, tentatively, truly, undeniably, under easy sail,
   undoubtedly, unequivocally, unhurriedly, unquestionably,
   very likely, voluptuously, well, with agonizing slowness,
   with deliberation, with ease, without difficulty