The third wheel意思

"The third wheel" is an English idiom that refers to an extra person or entity that is not needed or wanted in a particular situation, especially in the context of a romantic relationship. It suggests that the person is like an extra wheel on a bicycle, which is unnecessary and can be awkward or burdensome.

For example, if two people are on a date and a friend tags along uninvited, that friend might be described as "the third wheel." The phrase can also be used more generally to describe someone who interferes or intrudes where they are not wanted or needed.