语言学家对俚语没有简单明确的定义，但他们一致认为，俚语是一种不断变化的语言现象，存在于世界各地的亚文化中。俚语是一种非正式的词汇(单词、短语和语言用法)，常见于口头交谈，但在正式写作中避免使用。因为俚语并不总是从字面意义上讲得通，所以您需要熟悉每个俚语的意思和用法。英语俚语是日常英语的重要组成部分。
儒琴今日英语俚语 （English Slang of the Day)
third wheel （ also fifth wheel）（v & n）
英文解释
an unwanted, extra or unnecessary person ; someone who is in a situation where they are not needed or are ignored by most people；a person or thing that serves no useful purpose
中文解释
电灯泡、累赘; 冗员，不需要的人；无足轻重的人；陪衬
原文举例
Ivank Trump is third wheeling Trudeau，and his wife Sophie Gregoire. Canada’s top dawg was the man in the middle of Sophie Gregoire Trudeau and Ivanka Tuesday night at Fortune’s Most Powerful Women Summit and Gala in D.C.
Could’ve been a little awkward, since Ivanka and Trudeau have shared a few glances and stated how impressed they are with each other — but Sophie’s clearly the cool chick( cool girl), and seemed happy to have a hot third wheel.
Unclear if Jared Kushner attended. If he didn’t … big mistake, buddy. Huge.
伊万克·特朗普成为特鲁多的电灯泡。周二晚，在华盛顿举行的《财富》(Fortune)最具影响力女性峰会和晚宴上，加拿大的“顶级爱犬”特鲁多被夹在了索菲·格雷瓜尔·特鲁多(Sophie Gregoire Trudeau)和伊万卡(Ivanka)中间了。
这可能有点尴尬，因为伊万卡和特鲁多已经交换了几次眼色，并表示他们对彼此的印象有多深刻——但显然苏菲是一个很酷的女孩(酷女孩)，而且似乎很高兴有一个性感的电灯泡。
尚不清楚贾里德·库什纳(Jared Kushner)是否出席。如果他不……大错误,老兄。巨大的。
Martin O’Malley is clearly the third wheel at this debate. Even though there were only three Democrats onstage Saturday night, O’Malley still struggled to get much speaking time. The moderators didn’t ask him a direct question for nearly the first half-hour.
马丁·奥马利显然是这场辩论中的电灯泡。尽管周六晚上只有三名民主党人上台，奥马利仍然努力争取更多的演讲时间。主持人在前半个小时没有直接问他问题。
