inobservant

from The Collaborative International Dictionary of English v.0.48

Inobservant \In`ob*serv"ant\, a. [L. inobservans. See {In-} not,
   and {Observant}.]
   Not observant; regardless; heedless. --Bp. Hurd. --
   {In`ob*serv"ant*ly}, adv.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

34 Moby Thesaurus words for "inobservant":
      careless, disregardant, disregardful, distracted, distrait,
      heedless, inadvertent, inattentive, inconstant, incurious,
      indifferent, negligent, nonadherent, noncompliant, nonconforming,
      nonobservant, regardless, thoughtless, uncompliant, unconforming,
      unfaithful, unheedful, unheeding, unloyal, unmarking, unmindful,
      unnoticing, unnoting, unobservant, unobserving, unperceiving,
      unremarking, untrue, unwatchful