Definition of "tireless"

tireless¹

adjective
not comparable
1. Indefatigable, untiring and not yielding to fatigue
  Quotations
  James Milner's angled free-kick was headed on to the post by the tireless Bent and Lampard the opportunist was perfectly placed to stoop and head in from virtually on the goal-line.
  2011 November 12, “International friendly: England 1-0 Spain”, in BBC Sport‎

tireless²

adjective
not comparable
1. Without a tire (wheel covering); tyreless.