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A narrow opening, often cruciform, through which arrows might be discharged.

A narrow opening, often cruciform, through which arrows might be discharged.

bal-is-tr[=a]r'i-a, n. an aperture or loophole in the wall of a fortification through which crossbowmen might discharge their bolts.--n. BAL'ISTER (obs.), name for an arbalester or crossbowman, also an arbalest or crossbow itself. [Low L. ballistrarius, balistra, a variant form of ballista, a crossbow.]

Narrow apertures in the walls of a fortress, for the discharge of arrows from the cross-bow; often cruciform; thirteenth, fourteenth, and fifteenth centuries.