noun
portcullis
A heavy grating that can be lowered to block a castle gateway. Historical term; encountered in descriptions of Japanese castles and fortifications.
城門には落とし格子が設置されていた。
A portcullis was installed at the castle gate.
Compound of 落とし (otoshi, 'dropping') + 格子 (kōshi, 'lattice, grating'). The term literally describes a grating that is dropped to block an entrance.