voluntarily

from WordNet (r) 3.0 (2006)

voluntarily
    adv 1: out of your own free will; "he voluntarily submitted to
           the fingerprinting" [ant: {involuntarily}]

from The Collaborative International Dictionary of English v.0.48

Voluntarily \Vol"un*ta*ri*ly\, adv.
   In a voluntary manner; of one's own will; spontaneously.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

33 Moby Thesaurus words for "voluntarily":
      advisedly, by choice, by design, calculatedly, consciously,
      contemplatedly, deliberately, designedly, electively, freely,
      gratis, gratuitously, in cold blood, independently, intentionally,
      knowingly, meditatedly, on purpose, optionally, pointedly,
      premeditatedly, purposefully, purposely, purposively,
      spontaneously, willfully, willingly, with full intent, with intent,
      with malice aforethought, with purpose, without coercion,
      wittingly