The Collaborative International Dictionary of English v.0.48:

Tire iron \Tire" iron\, n.
   a short steel bar with one end flattened so as to form a
   blade, used to remove rubber tires from the rim of a wheel.
   [PJC]

WordNet (r) 3.0 (2006):

tire iron
    n 1: hand tool consisting of a lever that is used to force the
         casing of a pneumatic tire onto a steel wheel [syn: tire
         iron, tire tool]