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.