Source : Webster's Revised Unabridged Dictionary (1913)

Triplex \Tri"plex\, a. (Mach.)
   Havingthree principal operative parts or motions, so as to
   produce a three-fold effect.

Source : WordNet®

triplex
     adj : having three units or components or elements; "a ternary
           operation"; "a treble row of red beads"; "overcrowding
           made triple sessions necessary"; "triple time has three
           beats per measure"; "triplex windows" [syn: {ternary},
           {treble}, {triple}]