整流器 is a technical noun meaning 'rectifier' — an electronic device that converts alternating current (AC) to direct current (DC). It's a compound word: 整 (to arrange/rectify) + 流 (current/flow) + 器 (device/apparatus). You'll encounter it in electronics, engineering, and power-supply contexts. The English gloss 'commutator' is a false friend — a commutator is a different device (used in DC motors to reverse current direction), so stick with 'rectifier'.