The Collaborative International Dictionary of English v.0.48:

Pointlessly \Point"less*ly\, adv.
   Without point.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pointlessly
    adv 1: in a pointless manner; "he spent his life in pointlessly
           tiresome drudgery"

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "pointlessly":
   aimlessly, aridly, barrenly, bloodlessly, bootlessly, colorlessly,
   dismally, draggily, drearily, drearisomely, dryly, dully, dustily,
   effetely, emptily, fecklessly, fruitlessly, futilely, heavily,
   hollowly, inanely, insipidly, jejunely, lifelessly, needlessly,
   pallidly, ploddingly, ponderously, purposelessly, slowly,
   spiritlessly, stodgily, stuffily, superficially, tastelessly,
   tediously, to little purpose, to no purpose, uninterestingly,
   unnecessarily, uselessly, vainly, vapidly