The Collaborative International Dictionary of English v.0.48:

Combination \Com`bi*na"tion\, n. [LL. combinatio. See
   Combine.]
   1. The act or process of combining or uniting persons and
      things.
      [1913 Webster]

            Making new compounds by new combinations. --Boyle.
      [1913 Webster]

            A solemn combination shall be made
            Of our dear souls.                    --Shak.
      [1913 Webster]

   2. The result of combining or uniting; union of persons or
      things; esp. a union or alliance of persons or states to
      effect some purpose; -- usually in a bad sense.
      [1913 Webster]

            A combination of the most powerful men in Rome who
            had conspired my ruin.                --Melmoth.
      [1913 Webster]

   3. (Chem.) The act or process of uniting by chemical
      affinity, by which substances unite with each other in
      definite proportions by weight to form distinct compounds.
      [1913 Webster]

   4. pl. (Math.) The different arrangements of a number of
      objects, as letters, into groups.
      [1913 Webster]

   Note: In combinations no regard is paid to the order in which
         the objects are arranged in each group, while in
         variations and permutations this order is respected.
         --Brande & C.
         [1913 Webster]

   Combination car, a railroad car containing two or more
      compartments used for different purposes. [U. S.]

   Combination lock, a lock in which the mechanism is
      controlled by means of a movable dial (sometimes by
      several dials or rings) inscribed with letters or other
      characters. The bolt of the lock can not be operated until
      after the dial has been so turned as to combine the
      characters in a certain order or succession.

   Combination room, in the University of Cambridge, Eng., a
      room into which the fellows withdraw after dinner, for
      wine, dessert, and conversation.

   Combination by volume (Chem.), the act, process, or ratio
      by which gaseous elements and compounds unite in definite
      proportions by volume to form distinct compounds.

   Combination by weight (Chem.), the act, process, or ratio,
      in which substances unite in proportions by weight,
      relatively fixed and exact, to form distinct compounds.
      See Law of definite proportions, under Definite.

   Syn: Cabal; alliance; association; league; union;
        confederacy; coalition; conspiracy. See Cabal.
        [1913 Webster]

WordNet (r) 3.0 (2006):

combination
    n 1: a collection of things that have been combined; an
         assemblage of separate parts or qualities
    2: a coordinated sequence of chess moves
    3: a sequence of numbers or letters that opens a combination
       lock; "he forgot the combination to the safe"
    4: a group of people (often temporary) having a common purpose;
       "they were a winning combination"
    5: an alliance of people or corporations or countries for a
       special purpose (formerly to achieve some antisocial end but
       now for general political or economic purposes)
    6: the act of arranging elements into specified groups without
       regard to order
    7: the act of combining things to form a new whole [syn:
       combination, combining, compounding]

Moby Thesaurus II by Grady Ward, 1.0:

284 Moby Thesaurus words for "combination":
   Bund, Rochdale cooperative, accompaniment, accord, accordance,
   addition, adjunct, admixture, affairs, affiliation, affinity,
   agglomeration, agglutination, aggregate, aggregation, agreement,
   alignment, alliance, alloy, alloyage, amalgam, amalgamation,
   approximation, array, articulation, assemblage, assembly,
   association, axis, band, blend, blending, bloc, body, bond,
   bracketing, brew, building, buildup, cabal, cahoots, call-up,
   canvass, cartel, census, circle, clique, closeness, clustering,
   co-working, coaction, coadunation, coalescence, coalition,
   coincidence, collaboration, colleagueship, collection,
   collectivity, college, collegialism, collegiality, colligation,
   collocation, colloid, collusion, combine, combined effort, combo,
   comminglement, commingling, commixture, common market,
   communication, comparison, composite, composition, compound,
   comradeship, concatenation, concert, concerted action, concoction,
   concomitance, concordance, concourse, concurrence, confection,
   confederacy, confederation, confluence, conflux, confraternity,
   congeries, conglomerate, conglomeration, congregation, conjugation,
   conjunction, connectedness, connection, consilience, consolidation,
   consortium, conspiracy, constitution, construction,
   consumer cooperative, contiguity, contrariety, convergence,
   cooperation, cooperative, cooperative society, copartnership,
   copartnery, copulation, corps, corralling, correspondence, coterie,
   council, coupling, credit union, customs union, data-gathering,
   dealings, decoction, decoctum, deduction, disjunction, eclecticism,
   economic community, embodiment, emulsion, ensemble, fabrication,
   faction, fashioning, federation, fellowship, filiation, formation,
   fraternalism, fraternity, fraternization, free trade area,
   freemasonry, fusion, gang, gathering, getup, group, grouping,
   homology, hookup, identification, identity, immixture, inclusion,
   incorporation, individuality, indivisibility, ingathering,
   intactness, integrality, integration, integrity,
   intercommunication, intercourse, interfusion, interlarding,
   interlardment, interlinking, interminglement, intermingling,
   intermixture, intimacy, inventory, inviolability, irreducibility,
   joinder, joining, jointure, junction, juxtaposition, knotting,
   league, liaison, link, linkage, linking, machine, magma, make,
   makeup, marriage, meeting, melding, mergence, merger, merging,
   mingling, mix, mixing, mixture, mob, mobilization, mosaic, muster,
   mutual attraction, nearness, oneness, organic unity, organization,
   pairing, parasitism, particularity, partnership, party, paste,
   patchwork, piecing together, pluralism, political machine, pool,
   propinquity, proximity, purity, putting together, rapport,
   relatedness, relation, relations, relationship, ring, rodeo,
   roundup, saprophytism, selfsameness, set, setup, shaping,
   similarity, simplicity, simultaneity, singleness, singularity,
   society, sodality, solidarity, solidification, solidity, solution,
   sorority, splice, structure, structuring, survey, suspension,
   symbiosis, sympathy, synchronism, syncretism, syndicate,
   syndication, syneresis, synergy, synthesis, tie, tie-in, tie-up,
   togetherness, trust, undividedness, unification, uniformity, union,
   uniqueness, united action, unity, univocity, wholeness, yoking



The Free On-line Dictionary of Computing (30 December 2018):

combination

   1.  A set containing a certain number of
   objects selected from another set.

   The number of combinations of r objects chosen from a set of n
   is

   	n C r = n! / ((n-r)! r!)

   where "n C r" is normally with n and r as subscripts or as n
   above r in parentheses.

   See also permutation.

   2.  In the theory of combinators, a combination
   denotes an expression in which function application is the
   only operation.

   (1995-04-10)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

COMBINATION. A union of different things. A patent may be taken out for a
new combination of existing machinery, or machines. See 2 Mason, 112; and
Composition of matter.
     2. By combination is understood, in a bad sense, a union of men for the
purpose of violating the law.