The Collaborative International Dictionary of English v.0.48:

Tripartite \Trip"ar*tite\, a. [L. tripartitus; tri- (see Tri-)
   + partitus, p. p. of partiri to part, to divide. See Part,
   v. i.]
   1. Divided into three parts; triparted; as, a tripartite
      leaf.
      [1913 Webster]

   2. Having three corresponding parts or copies; as, to make
      indentures tripartite. --A. Smith.
      [1913 Webster]

   3. Made between three parties; as, a tripartite treaty.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tripartite
    adj 1: involving three parties or elements; "a tripartite
           treaty"; "a tripartite division"; "a three-way playoff"
           [syn: tripartite, three-party, three-way]