Source : Webster's Revised Unabridged Dictionary (1913)

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

Source : WordNet®

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