The Collaborative International Dictionary of English v.0.48:

Conjugation \Con`ju*ga"tion\, n. [L. conjugatio conjugation (in
   senses 1 & 3).]
   1. the act of uniting or combining; union; assemblage. [Obs.]
      [1913 Webster]

            Mixtures and conjugations of atoms.   --Bentley.
      [1913 Webster]

   2. Two things conjoined; a pair; a couple. [Obs.]
      [1913 Webster]

            The sixth conjugations or pair of nerves. --Sir T.
                                                  Browne.
      [1913 Webster]

   3. (Gram.)
      (a) The act of conjugating a verb or giving in order its
          various parts and inflections.
      (b) A scheme in which are arranged all the parts of a
          verb.
      (c) A class of verbs conjugated in the same manner.
          [1913 Webster]

   4. (Biol.) A kind of sexual union; -- applied to a blending
      of the contents of two or more cells or individuals in
      some plants and lower animals, by which new spores or
      germs are developed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

conjugation
    n 1: the state of being joined together [syn: junction,
         conjunction, conjugation, colligation]
    2: the inflection of verbs
    3: the complete set of inflected forms of a verb
    4: a class of verbs having the same inflectional forms
    5: the act of pairing a male and female for reproductive
       purposes; "the casual couplings of adolescents"; "the mating
       of some species occurs only in the spring" [syn: coupling,
       mating, pairing, conjugation, union, sexual union]
    6: the act of making or becoming a single unit; "the union of
       opposing factions"; "he looked forward to the unification of
       his family for the holidays" [syn: union, unification,
       uniting, conjugation, jointure] [ant: disunion]

Moby Thesaurus II by Grady Ward, 1.0:

172 Moby Thesaurus words for "conjugation":
   Anschluss, IC analysis, Janus, abutment, abuttal, accidence,
   addition, adjacency, adjoiningness, affiliation, affix, affixation,
   agglomeration, agglutination, aggregation, agreement, alliance,
   allomorph, amalgamation, ambiguity, ambivalence, apposition,
   appulse, articulation, artificial insemination, assimilation,
   association, biformity, bifurcation, blend, blending, bond,
   bound morpheme, bracketing, cabal, cartel, centralization,
   clustering, coalescence, coalition, combination, combine, combo,
   communication, composition, concatenation, concourse, concurrence,
   confederacy, confederation, confluence, congeries, conglomeration,
   conjunction, connection, consolidation, conspiracy,
   conterminousness, contiguity, convergence, copulation,
   coterminousness, coupling, cross-fertilization, cross-pollination,
   cutting, declension, derivation, dichotomy, difference of form,
   doubleness, doublethink, doubling, dualism, duality, duplexity,
   duplication, duplicity, ecumenism, embodiment, enclitic,
   encompassment, enosis, equivocality, fecundation, federalization,
   federation, fertilization, formative, free form, fusion, gathering,
   getting with child, halving, heterogamy, hookup,
   immediate constituent analysis, impregnation, inclusion,
   incorporation, infix, infixation, inflection, insemination,
   integration, intercommunication, intercourse, interlinking, irony,
   isogamy, joinder, joining, jointure, junction, junta,
   juxtaposition, knotting, league, liaison, linkage, linking,
   marriage, meeting, meld, melding, merger, merging, morph, morpheme,
   morphemic analysis, morphemics, morphology, morphophonemics,
   orthogamy, package, package deal, pairing, paradigm, perigee,
   perihelion, polarity, pollination, pollinization, prefix,
   prefixation, proclitic, radical, root, solidification, splice,
   stem, suffix, suffixation, symbiosis, syncretism, syndication,
   syneresis, synthesis, syzygy, theme, tie, tie-in, tie-up, twinning,
   two-facedness, twoness, unification, union, wedding,
   word-formation, yoking, zygosis