Source : Webster's Revised Unabridged Dictionary (1913)

Prolongation \Pro`lon*ga"tion\, n. [F. prolongation.]
   1. The act of lengthening in space or in time; extension;
      protraction. --Bacon.

   2. That which forms an additional length.

Source : WordNet®

prolongation
     n 1: the act of prolonging something; "there was an indefinite
          prolongation of the peace talks" [syn: {protraction}, {perpetuation},
           {lengthening}]
     2: amount or degree or range to which something extends; "the
        wire has an extension of 50 feet" [syn: {extension}, {lengthiness}]
     3: the consequence of being lengthened in duration [syn: {lengthiness},
         {continuation}, {protraction}]