Battlements: A parapet with indentations and raised portions. Battlements are sometimes called crenellations.
Buttress: Projection from the wall that provides extra support for the building.
Drum tower: A large circular tower that was usually low and squat.
Fosse: A ditch surrounding the castle.
Garderobe: A castle toilet. The garderobe was often a projection from the wall over the moat.
Portcullis: Grating made of metal and wood.
Solar: The upper living room of a castle.
Parapet: A low wall on the outer side of the main wall.
Rampart: A defensive stone or earth wall surrounding a castle.
Shell-keep: A wall surrounding the inner portion of the castle.
Moat: A deep wide trench round a castle.
Machicolations: Projecting stonework on the outside of castle towers or walla, will hole in floor for dropping missiles on people attacking the castle.
Wall-walk: A passage along the castle wall.