Noun
(military, historical) The outer wall of a castle or defensive wall between two bastions.
(architecture) The non-load-bearing outer skin of a modern building.
Source: en.wiktionary.orgAdmittedly the southwestern parts of the building of the baroque Dresden Zwinger including the Kronentor gate stand on parts of the outer curtain wall that are still visible today; but there is no longer any trace of the inner wall. Source: Internet
An earthen bank could be piled behind a castle's curtain wall to absorb some of the shock of impact. Source: Internet
Its outer defenses consist of a huge curtain wall, convert tall and convert thick on its thinnest side, nearly convert thick on its seaward side. Source: Internet
It made approaching the curtain wall of the castle more difficult and the undermining of the wall virtually impossible. Source: Internet
Its purpose was twofold; to stop devices such as siege towers from reaching the curtain wall and to prevent the walls from being undermined. Source: Internet
King Christian III had the corners of the curtain wall supplemented with bastions in 1558-59. Source: Internet