Source : Webster's Revised Unabridged Dictionary (1913)

Radial engine \Radial engine\ (Mach.)
   An engine, usually an internal-combustion engine of a certain
   type (the

   {radial type}) having several cylinders arranged radially
      like the spokes of a complete wheel. The

   {semiradial engine} has radiating cylinders on only one side
      of the crank shaft.

Source : WordNet®

radial engine
     n : an internal-combustion engine having cylinders arranged
         radially around a central crankcase [syn: {rotary engine}]