N-COUNT; N-IN-NAMES 堡垒;要塞;城堡 A fort is a strong building or a place with a wall or fence around it where soldiers can stay and be safe from the enemy.

PHRASE 替人照料;代为负责 If you hold the fort for someone, or, in American English, if you hold down the fort, you look after things for them while they are somewhere else or are busy doing something else.