The Collaborative International Dictionary of English v.0.48:

Battlement \Bat"tle*ment\ (-ment), n. [OE. batelment; cf. OF.
   bataillement combat, fr. batailler, also OF. bastillier,
   bateillier, to fortify. Cf. Battle, n., Bastile,
   Bastion.] (Arch.)
   (a) One of the solid upright parts of a parapet in ancient
       fortifications.
   (b) pl. The whole parapet, consisting of alternate solids and
       open spaces. At first purely a military feature,
       afterwards copied on a smaller scale with decorative
       features, as for churches.
       [1913 Webster]

WordNet (r) 3.0 (2006):

battlement
    n 1: a rampart built around the top of a castle with regular
         gaps for firing arrows or guns [syn: battlement,
         crenelation, crenellation]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "battlement":
   abatis, advanced work, balistraria, bank, banquette,
   barbed-wire entanglement, barbican, barricade, barrier, bartizan,
   bastion, breastwork, bulwark, casemate, castellation,
   cheval-de-frise, circumvallation, contravallation, counterscarp,
   crenel, curtain, demibastion, dike, drawbridge, earthwork,
   embrasure, enclosure, entanglement, escarp, escarpment, fence,
   fieldwork, fortalice, fortification, glacis, loophole, lunette,
   machicolation, mantelet, merlon, mound, outwork, palisade, parados,
   parapet, portcullis, postern gate, rampart, ravelin, redan,
   redoubt, sally port, scarp, sconce, stockade, tenaille, vallation,
   vallum, work



Easton's 1897 Bible Dictionary:

Battlement
   a parapet wall or balustrade surrounding the flat roofs of the
   houses, required to be built by a special law (Deut. 22:8). In
   Jer. 5:10, it denotes the parapet of a city wall.