The Collaborative International Dictionary of English v.0.48:

Conjoint \Con*joint"\, a. [F. conjoint, p. p. of conjoindre. See
   Conjoin, and cf. Conjunct.]
   United; connected; associated. "Influence conjoint."
   --Glover.
   [1913 Webster]

   Conjoint degrees (Mus.), two notes which follow each other
      immediately in the order of the scale, as ut and re.
      --Johnson.

   Conjoint tetrachords (Mus.), two tetrachords or fourths,
      where the same note is the highest of one and the lowest
      of the other; -- also written conjunct.
      [1913 Webster]