noun
signal flare; pyrotechnic signal
Refers to a device that produces a bright light or smoke for signaling, often used in emergencies or military contexts.
遭難者は信号弾を打ち上げて救助を求めた。
The survivors fired a signal flare to call for rescue.
軍の演習で信号弾が使われた。
Signal flares were used in the military exercise.
発煙筒 is a smoke canister, often used for signaling or marking, but 信号弾 typically refers to a projectile that produces light or smoke.
Compound of 信号 (signal) and 弾 (projectile, bullet). The exact historical derivation is uncertain, but the word transparently means 'signal projectile'.