groundless

groundless
    adj 1: without a basis in reason or fact; "baseless gossip";
           "the allegations proved groundless"; "idle fears";
           "unfounded suspicions"; "unwarranted jealousy" [syn:
           {baseless}, {groundless}, {idle}, {unfounded},
           {unwarranted}, {wild}]
    

Groundless \Ground"less\, a. [AS. grundle['a]s bottomless.]
   Without ground or foundation; wanting cause or reason for
   support; not authorized; false; baseless; as, groundless
   fear; a groundless report, rumor, or assertion. --
   {Ground"less*ly}, adv. -- {Ground"less*ness}, n.
    

58 Moby Thesaurus words for "groundless":
      baseless, bottomless, built on sand, chimerical, empty, flimsy,
      gratuitous, hypothetical, idle, ill-founded, illusory, imaginary,
      inconclusive, indecisive, not following, not proved,
      not well-founded, speculative, suppositional, tenuous,
      unascertained, unattested, unauthenticated, unbased, uncalled-for,
      uncertified, unconfirmed, uncorroborated, undemonstrated,
      undetermined, unestablished, unfixed, unfounded, ungrounded,
      unjustifiable, unjustified, unproved, unproven, unreasonable,
      unsettled, unshown, unsound, unsubstantiated, unsupportable,
      unsupported, unsupported by evidence, unsustainable, unsustained,
      untenable, untested, untried, unvalidated, unverified, unwarranted,
      vain, without basis, without foundation, without grounds