The Collaborative International Dictionary of English v.0.48:

Usucaption \U`su*cap"tion\ (?; 277), n. [L. usucapere,
   usucaptum, to acquire by long use; usu (ablative of usus use)
   + capere to take: cf. usucapio usucaption.] (Roman Law)
   The acquisition of the title or right to property by the
   uninterrupted possession of it for a certain term prescribed
   by law; -- the same as prescription in common law.
   [1913 Webster]

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

USUCAPTION, civil law. The manner of acquiring property in things by the
lapse of time required by law.
     2. It differs from prescription, which has the same sense, and means,
in addition, the manner of acquiring and losing, by the effect of time
regulated by law, all sorts of rights and actions. Merl. Repert. mot
Prescription, tom. xii. page 671; Ayl. Pand. 320; Wood's Inst. Civ. Law,
165; Lecons Elem. du Dr. Rom. Sec. 437; 1 Browne's Civ. Law, 264, n.;
vattel, ii. 2, c. 2, Sec. 140.