a pin passed through the end of an axle to keep a wheel in position 制轮楔
a person or thing vital to an enterprise or organization (企业、组织中的)至关重要的人物;关键因素 regular brushing is the linchpin of all good dental hygiene. 经常刷牙是保持牙齿卫生的关键。
语源
late Middle English: from Old English lynis (in the sense 'linchpin') + pin