Definition:
"Third wheel" is a slang term used to describe someone who is hanging out with two people who are romantically involved, making them the extra or unwanted person in the group.
Use case:
You can use the term "third wheel" when you feel like you are intruding on a couple's time together or when someone else is intruding on your time with your significant other. For example, if you are out with your best friend and their partner, and you feel like you are not really needed or wanted, you could say, "I feel like a third wheel here."
• I don't want to be the third wheel when my friends go out tonight, so I'm going to stay home and catch up on some Netflix.
• When my sister and her husband invited me to come on vacation with them, I was worried I'd be the third wheel, but they made me feel like part of the family.
• I hate being the third wheel on a date, but sometimes my roommate needs me to cover for her when she's running late.
• Being the third wheel at a party can be awkward, but if you can find someone else who's feeling left out, you might just make a new friend.
• My cousin is always the third wheel when she hangs out with me and my best friend, but we try to include her in everything we do.
• I'm always the third wheel when I hang out with my best friend and her boyfriend, but I don't mind because they're such a fun couple to be around.