The Collaborative International Dictionary of English v.0.48:

Jointure \Join"ture\, n. [F. jointure a joint, orig., a joining,
   L. junctura, fr. jungere to join. See Join, and cf.
   Juncture.]
   [1913 Webster]
   1. A joining; a joint. [Obs.]
      [1913 Webster]

   2. (Law) An estate settled on a wife, which she is to enjoy
      after husband's decease, for her own life at least, in
      satisfaction of dower.
      [1913 Webster]

            The jointure that your king must make,
            Which with her dowry shall be counterpoised. --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jointure \Join"ture\, v. t. [imp. & p. p. Jointured; p. pr. &
   vb. n. Jointuring.]
   To settle a jointure upon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

jointure
    n 1: (law) an estate secured to a prospective wife as a marriage
         settlement in lieu of a dower [syn: jointure, legal
         jointure]
    2: 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:

56 Moby Thesaurus words for "jointure":
   agglomeration, agglutination, aggregation, appanage, articulation,
   bond, bracketing, clustering, combination, communication,
   concatenation, concourse, congeries, conglomeration, conjugation,
   conjunction, connection, convergence, copulation, coupling, dot,
   dower, dowry, endowment, foundation, gathering, hookup,
   intercommunication, intercourse, interlinking, investment, joinder,
   joining, junction, knotting, legal jointure, liaison, linkage,
   linking, marriage, marriage portion, meeting, merger, merging,
   pairing, portion, settlement, splice, symbiosis, thirds, tie,
   tie-in, tie-up, unification, union, yoking



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

JOINTURE, estates.. A competent livelihood of freehold for the wife, of
lands and tenements; to take effect in profit or possession, presently after
the death of the husband, for the life of the wife at least.
     2. Jointures are regulated by the statute of 27 Hen. VIII. o. 10,
commonly called the statute of uses.
     3. To make a good jointure, the following circumstances must concur,
namely; 1. It must take effect, in possession or profit, immediately from
the death of the husband. 2. It must be for the wife's life, or for some
greater estate. 3. It must be limited to the wife herself, and not to any
other person in trust for her. 4. It must be made in satisfaction for the
wife's whole dower, and not of part of it only. 5. The estate limited to the
wife must be expressed or averred to be, in satisfaction of her whole dower.
6. It must be made before marriage. A jointure attended with all these
circumstances is binding on the widow, and is a complete bar to the claim of
dower; or rather it prevents its ever arising. But there are other. modes of
limiting an estate to a wife, which, Lord Coke says, are good jointures
within the statute, provided the wife accepts of them after the death of the
husband. She may, however, reject them, and claim her dower. Cruise, Dig.
tit. 7; 2 Bl. Com. 137; Perk. h.t. In its more enlarged sense, a jointure
signifies a joint estate, limited to both husband and. wife. 2 131. Com.
137. Vide 14 Vin. Ab. 540; Bac. Ab. h.t.; 2 Bouv. Inst. n. 1761, et seq.