portcullis

n. heavy metal grating at the entrance to a fortress

A portcullis is a grille or gate made of wood, metal or a combination of the two.Portcullises fortified the entrances to many medieval castles, acting as a last line of defence during time of attack or siege. Each portcullis was mounted in vertical grooves in castle walls and could be raised or lowered quickly by means of chains or ropes attached to an internal winch. There would often be two portcullises to the main entrance. The one closest to the inside would be closed first and then the one furthest away. This was used to trap the enemy and often, burning wood or hot oil would be poured onto them from the roof. Also, archers could shoot arrows at the trapped enemies. There were often arrow holes in the sides of the walls for archers and crossbowman to eliminate the besieging army.
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Noun
1. gate consisting of an iron or wooden grating that hangs in the entry to a castle or fortified town; can be lowered to prevent passage
(hypernym) gate

(v. t.)
To obstruct with, or as with, a portcullis; to shut; to bar.
  

(n.)
An English coin of the reign of Elizabeth, struck for the use of the East India Company; -- so called from its bearing the figure of a portcullis on the reverse.
  

(n.)
A grating of iron or of timbers pointed with iron, hung over the gateway of a fortress, to be let down to prevent the entrance of an enemy.
  

A heavy wooden or metal gate that closed an entrance to a castle . Portcullises were generally controlled from an interior room on the gatehouse, raising and lowering it as required.