The Collaborative International Dictionary of English v.0.48:

Measureless \Meas"ure*less\, a.
   Without measure; unlimited; immeasurable. --
   Meas"ure*less*ness, n.
   [1913 Webster]

         Where Alf, the sacred river ran,
         Through canyons measureless to man,
         Down to a hidden sea.                    --Coleridge.
   [PJC]

   Syn: Boundless; limitless; endless; unbounded; unlimited;
        vast; immense; infinite; immeasurable.
        [1913 Webster]

WordNet (r) 3.0 (2006):

measureless
    adj 1: without limits in extent or size or quantity; "limitless
           vastness of our solar system" [syn: illimitable,
           limitless, measureless]