The Collaborative International Dictionary of English v.0.48:

Messuage \Mes"suage\ (?; 48), n. [Cf. OF. mesuage, masnage, LL.
   messuagium, mansionaticum, fr. L. mansio, -onis, a staying,
   remaining, dwelling, fr. manere, mansum, to stay, remain, E.
   mansion, manse.] (Law)
   A dwelling house, with the adjacent buildings and curtilage,
   and the adjoining lands appropriated to the use of the
   household. --Cowell. Bouvier.
   [1913 Webster]

         They wedded her to sixty thousand pounds,
         To lands in Kent, and messuages in York. --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

messuage
    n 1: (law) a dwelling house and its adjacent buildings and the
         adjacent land used by the household

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

MESSUAGE, property. This word is synonymous with dwelling-house; and a grant
of a messuage with the appurtenances, will not only pass a house, but all
the buildings attached or belonging to it, as also its curtilage, garden and
orchard, together with the close on which the house is built. 1 Inst. 5, b.;
2 Saund. 400; Ham. N. P. 189; 4 Cruise, 321; 2 T. R. 502; 1 Tho. Co. Litt.
215, note 35; 4 Blackf. 331. But see the cases cited in 9 B. & Cress. 681;
S. C. 17 Eng. Com. L. R. 472. This term, it is said, includes a church. 11
Co. 26; 2 Esp. N. P. 528; 1 Salk. 256; 8 B. & Cress. 25; S. C. 15 Eng. Com.
L. Rep. 151. Et vide 3 Wils. 141; 2 Bl. Rep. 726; 4 M. & W. 567; 2 Bing. N.
C. 617; 1 Saund. 6.