life preserver

life-preserver的词性：
n.（名词）

1. A buoyant device, usually in the shape of a ring, belt, or jacket, designed to keep a person afloat in the water.
救生用具：一种有浮力的装置，通常是圈状、带状或夹克衫状，用途是使人能浮在水中

2. Chiefly British A weapon, such as a blackjack.
【多用于英国】 护身棒：一种武器，如装有手柄的包革金属棒