Wordnet 3.0
NOUN (1)
1. 
 one of three copies; 
 any of three things that correspond to one another exactly; 
VERB (1)
1. 
 reproduce threefold; 
- Example: "triplicate the letter for the committee"
The Collaborative International Dictionary of English v.0.48:
Triplicate \Trip"li*cate\, a. [L. triplicatus, p. p. of
   triplicare to triple, treble; tri- (see Tri-) + plicare to
   fold. See Ply, v. t.]
   Made thrice as much; threefold; tripled.
   [1913 Webster]
   Triplicate ratio (Math.), the ratio of the cubes of two
      quantities; thus, the triplicate ratio of a to b is a^3:
      b^3.
      [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Triplicate \Trip"li*cate\, n.
   A third thing corresponding to two others of the same kind.
   [1913 Webster]
WordNet (r) 3.0 (2006):
triplicate
    n 1: one of three copies; any of three things that correspond to
         one another exactly
    v 1: reproduce threefold; "triplicate the letter for the
         committee"
Moby Thesaurus II by Grady Ward, 1.0:
48 Moby Thesaurus words for "triplicate":
   Photostat, Xerox, clone, copy, counterpart, cube, ditto, double,
   dupe, duplicate, duplication, facsimile, hectograph, manifold,
   microcopy, microfilm, mimeo, mimeograph, model, multigraph,
   multiply by three, quadruplicate, reduplicate, repetition, replica,
   replicate, replication, representation, reproduce, reproduction,
   second carbon, stat, tern, ternal, ternary, ternate, three-ply,
   threefold, trace, transcribe, treble, trilogic, trinal, trine,
   triple, triplex, triplication, triplicity