third wheel(redirected from 3rd)
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Someone who has no real place or purpose in a situation, likened to a superfluous extra wheel on a two-wheeled vehicle. When Kelly invited me to go to the movies, I didn't know that her boyfriend would be joining us. I felt like a third wheel the entire night.
a fifth/third ˈwheel(American English) an unwanted, extra or unnecessary person: No, I don’t think I’ll join you. Whenever I go out with you guys I just feel like a fifth wheel.
This refers to adding an extra unnecessary wheel to a vehicle.
n. an extra person; a person who gets in the way. (see also spare tire.) Well, let’s face it. We don’t need you. You are a third wheel.