The Collaborative International Dictionary of English v.0.48:

Aimless \Aim"less\, a.
   Without aim or purpose; as, an aimless life. --
   Aim"less*ly, adv. -- Aim"less*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

aimlessly
    adv 1: without aim; in an aimless manner; "he wandered around
           aimlessly"

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "aimlessly":
   anarchically, at haphazard, at hazard, at random, bootlessly,
   casually, chaotically, confusedly, dispersedly, dysteleologically,
   fecklessly, fruitlessly, futilely, haphazardly, indiscriminately,
   inexplicably, insignificantly, meaninglessly, needlessly,
   nonconnotatively, nondenotatively, nonsensically, planlessly,
   pointlessly, promiscuously, purposelessly, randomly, riotously,
   senselessly, stochastically, to little purpose, to no purpose,
   turbulently, unaccountably, unmeaningly, unnecessarily,
   unsignificantly, uselessly, vaguely, vainly, wanderingly