CURTAIN, or COURTIN, in fortification, is that part of the rampart of a place which is betwixt the flanks of two battions, bordered with a parapet five feet high, behind which the soldiers stand to fire upon the covered way and into the moat.

CURVATOR coccygis, in anatomy. See Vol. I., p. 220.

CURVATURE of a line, is the peculiar manner of its bending or flexure by which it becomes a curve of such and such peculiar properties.