Source : Webster's Revised Unabridged Dictionary (1913)

Quadruplet \Quad"ru*plet\, n. [From {Quadruple}.]
   1. A collection or combination of four of a kind.

   2. pl. Four children born in the same labor.

   3. A cycle for carrying four riders, so arranged that all the
      reders can assist in the propulsion.

Source : WordNet®

quadruplet
     n 1: the cardinal number that is the sum of three and one [syn: {four},
           {4}, {IV}, {tetrad}, {quatern}, {quaternion}, {quaternary},
           {quaternity}, {quartet}, {foursome}, {Little Joe}]
     2: one of four children born at the same time from the same
        pregnancy [syn: {quad}]
     3: a set of four similar things considered as a unit [syn: {quartet},
         {quartette}]