The Collaborative International Dictionary of English v.0.48:

Tenement \Ten"e*ment\, n. [OF. tenement a holding, a fief, F.
   t[`e]nement, LL. tenementum, fr. L. tenere to hold. See
   Tenant.]
   1. (Feud. Law) That which is held of another by service;
      property which one holds of a lord or proprietor in
      consideration of some military or pecuniary service; fief;
      fee.
      [1913 Webster]

   2. (Common Law) Any species of permanent property that may be
      held, so as to create a tenancy, as lands, houses, rents,
      commons, an office, an advowson, a franchise, a right of
      common, a peerage, and the like; -- called also free
      tenements or frank tenements.
      [1913 Webster]

            The thing held is a tenement, the possessor of it a
            "tenant," and the manner of possession is called
            "tenure."                             --Blackstone.
      [1913 Webster]

   3. A dwelling house; a building for a habitation; also, an
      apartment, or suite of rooms, in a building, used by one
      family; often, a house erected to be rented.
      [1913 Webster]

   4. Fig.: Dwelling; abode; habitation.
      [1913 Webster]

            Who has informed us that a rational soul can inhabit
            no tenement, unless it has just such a sort of
            frontispiece?                         --Locke.
      [1913 Webster]

   5. A tenement house.
      [PJC]

   Tenement house, commonly, a dwelling house erected for the
      purpose of being rented, and divided into separate
      apartments or tenements for families. The term is often
      applied to apartment houses occupied by poor families,
      often overcrowded and in poor condition.
      [1913 Webster +PJC]

   Syn: House; dwelling; habitation.

   Usage: Tenement, House. There may be many houses under
          one roof, but they are completely separated from each
          other by party walls. A tenement may be detached by
          itself, or it may be part of a house divided off for
          the use of a family. In modern usage, a tenement or
          tenement house most commonly refers to the meaning
          given for tenement house, above.
          [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

tenement
    n 1: a run-down apartment house barely meeting minimal standards
         [syn: tenement, tenement house]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "tenement":
   Augean stables, acres, apartment, apartment house, chambers,
   chattels real, cold-water flat, condominium,
   cooperative apartment house, demesne, domain, dump, duplex,
   duplex apartment, duplex house, flat, flats, garden apartment,
   grounds, high-rise apartment building, hole, honor, hovel, land,
   landed property, lands, lodgings, lot, lots, manor, messuage,
   parcel, penthouse, pesthole, pigpen, pigsty, plague spot, plat,
   plot, praedium, property, quadrat, railroad flat, real estate,
   real property, realty, rental, rookery, rooms, set of rooms, slum,
   stable, sty, suite, tenements, the slums, toft, warren



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

TENEMENT, estates. In its most extensive signification tenement comprehends
every thing which may be holden, provided it be of a permanent nature; and
not only lands and inheritances which are holden, but also rents and profits
a prendre of which a man has any frank tenement, and of which he may be
seised ut de libero tenemento, are included under this term. Co. Litt. 6 a;
1 Tho. Co. Litt. 219; Pork. s. 114; 2 Bl. Com. 17. But the word tenements
simply, without other circumstances, has never been construed to pass a fee.
10 Wheat. 204. In its more confined and vulgar acceptation, it means a house
or building. Ibid. an 1 Prest. on Est. 8. Vide 4 Bing. 293; S C. l1 Eng. C.
L. Rep. 207; 1 T. R. 358; 3 T. R. 772; 3 East, R. 113; 5 East, R. 239;
Burn's Just. Poor, 525 to 541; 1 B. & Adolph. 161; S. C. 20 Eng. C. L. Rep.
36 8; Com. Dig. Grant, E 2; Trespass, A 2; Wood's Inst. 120; Babington on
Auctions, 211, 212.