noun
catapult; ballista; mangonel; onager; trebuchet
Refers to various historical or fantasy siege weapons that hurl stones or other projectiles. The specific type is often clear from context or additional description.
中世の城攻めでは投石機がよく使われた。
Catapults were often used in medieval castle sieges.
このゲームでは投石機で敵の壁を破壊できる。
In this game, you can destroy enemy walls with a catapult.
noun
Only when written 投石器
Specifically refers to a hand-held sling or slingshot for throwing stones. This sense is restricted to the kanji form 投石器.
古代の兵士は投石器で石を飛ばした。
Ancient soldiers hurled stones with slings.
子供の頃、投石器を作って遊んだ。
When I was a child, I made a slingshot and played with it.
Compound of 投石 (stone throwing) + 機 (machine) or 器 (device). The exact historical derivation is uncertain; the spellings are conventionally associated with siege engines and slings respectively.