The Collaborative International Dictionary of English v.0.48:

Improperly \Im*prop"er*ly\, adv.
   In an improper manner; not properly; unsuitably;
   unbecomingly.
   [1913 Webster]

WordNet (r) 3.0 (2006):

improperly
    adv 1: in an improper way; "he checked whether the wound had
           healed improperly" [ant: decent, decently, in good
           order, properly, right, the right way]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "improperly":
   abominably, agonizingly, awfully, baldly, balefully, bitterly,
   blatantly, brashly, coarsely, confoundedly, crassly, crudely,
   cruelly, damnably, deadly, deathly, deucedly, distressingly,
   dolorously, dreadfully, egregiously, excessively, excruciatingly,
   exorbitantly, extravagantly, flagrantly, frightfully, grievously,
   grossly, hellishly, horribly, incorrectly, indecently,
   indecorously, indelicately, inelegantly, inexcusably, infernally,
   inordinately, intolerably, lamentably, miserably, nakedly,
   offensively, openly, painfully, piteously, ribaldly, roughly,
   rudely, sadly, shatteringly, shockingly, something awful,
   something fierce, sorely, staggeringly, terribly, torturously,
   unashamedly, unbearably, unconscionably, uncouthly, unduly,
   unpardonably, unseemly, untastefully, vulgarly, woefully, wrong,
   wrongfully, wrongly