noun
fixed artillery; fixed gun
Military term for artillery pieces or guns permanently mounted in a fixed position, as opposed to mobile or towed artillery.
要塞には固定砲が設置されていた。
Fixed artillery was installed in the fortress.
要塞砲 is fortress artillery, often fixed, but 固定砲 is a broader term for any fixed gun, not limited to fortresses.
Compound of 固定 (こてい, 'fixed') and 砲 (ほう, 'gun, artillery').