noun
propeller; propulsion device
Technical term for a device that generates thrust, such as a ship's propeller or an aircraft's propeller.
船の推進器が故障した。
The ship's propeller broke down.
この飛行機は推進器を二つ備えている。
This aircraft is equipped with two propellers.
スクリュー often refers specifically to a ship's screw propeller, whereas 推進器 is a broader term for any propulsion device.
Compound of 推進 (propulsion) + 器 (device). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese technical compounding pattern.