美 [fɪfθ wiːl]
第五个轮子：指马车前轴上的一个水平轮子或轮子的一部分，由两个部分在彼此之上旋转，用于支撑以防止翻倒。
多余的、不必要的或累赘的人或物：指那些多余、不必要或累赘的人或物。
fifth wheel //
名词 a spare wheel for a four-wheeled vehicle 备用轮
第五个轮子；备用轮；多余的人
... four-letter words 四字母禁忌词 fifth wheel 备用轮；多余的人或物 six of one and half a dozen of the other 半斤八两，不相上下 ...
衔接套牢前面卡车与后面RV拖车(或是前面重型联结卡车与后面货运拖车)的圆轮状凹槽装置，就是所谓的“第五轮”(Fifth Wheel)。
... Fifth Columnist 第五纵队队员 fifth wheel 多余人 fifth 第五的 ...
I'm tired of being treated like the fifth wheel around here .
在这儿工作，我感觉自己只是一个旋转不停的齿轮。
I am tired of being treated like the fifth wheel around here.
我讨厌在这儿被当作多余的东西。
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。
Ted Scott, the American Trucking Association's director of engineering, said an automatic locking device secures the pin into the fifth wheel.
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.
"It is possible that with an old, not properly maintained fifth wheel that the device can get loose, the sides can wear away, the hole that the pin fits into is no longer snug and rigid, " Scott said.