a fifth wheel
常见例句
- A car does not need a fifth wheel.
一辆车通常不需要第五只轮子。 - By definition, a fifth wheel is a wheel or a portion of a wheel with two parts rotating on each other that sits on the front axle of a carriage and adds extra support so it doesn’t tip.
通过定义，第五个轮子，是成为一个四轮马车的前车轴上互相旋转的两个部分的一个轮子或一个轮子的一部分，而加上一个额外的辅助轮子，这样它就不会倾斜。 - He was the only one without a date, so he felt like a fifth wheel.
他是唯一没被邀请的人，因此他感到自己很是多余。 - Trailers are typically attached to tractors by a "fifth wheel, " in which a coupling pin on the trailer fits into the center of a large horseshoe-shaped piece of metal.
NPR: Runaway Trailer Crashes Rare; NY Accident Killed 7 返回 a fifth wheel