Source : Webster's Revised Unabridged Dictionary (1913)

Override \O`ver*ride"\, v. t. [imp. {Overrode}; p. p.
   {Overridden}, {Overrode}, {Overrid}; p. pr. & vb. n.
   {Overriding}.] [AS. offer[=i]dan.]
   1. To ride over or across; to ride upon; to trample down.

            The carter overridden with [i. e., by] his cart.
                                                  --Chaucer.

   2. To suppress; to destroy; to supersede; to annul; as, one
      low overrides another; to override a veto.

   3. To ride beyond; to pass; to outride. [Obs.]

            I overrode him on the way.            --Shak.

   4. To ride too much; to ride, as a horse, beyond its
      strength.

Source : WordNet®

override
     n 1: a manually operated device to correct the operation of an
          automatic device
     2: the act of nullifying; making null and void; counteracting
        or overriding the effect or force of something [syn: {nullification}]
     v 1: rule against; "The Republicans were overruled when the House
          voted on the bill" [syn: {overrule}, {overturn}, {overthrow},
           {reverse}]
     2: prevail over; "health considerations override financial
        concerns"
     3: counteract the normal operation of (an automatic gear shift
        in a vehicle)
     4: ride (a horse) too hard
     [also: {overrode}, {overridden}]