A fork of Rural Dictionary
The person in a group of people (usually two, though sometimes more) who is most often left out of things.
The third wheel is usually there for one of two reasons - to act as a mediator, such as with a couple, or to be the "convenience friend" when nobody else is there to hang.
Third wheels are not normally forcefully excluded from activities, but they're not usually invited or informed about them either.
Not to be confused with being third-wheeled.
Jim left the friend group because he was sick of being excluded as a third wheel.
To be third-wheeled is to be intentionally left out of activities as part of a friend group. If you're third-wheeled, you're most definitely the convenience friend. They'll make you desperate to hang out, but never actually include you in anything. You can expect to be asked to hang out only if nobody else wants to.
If you notice you're being third-wheeled, it's probably a toxic friendship and you should get out of there.
Jim was third-wheeled by his friends so they always had someone to fall back to when they got bored.