third

a fifth/third wheel (American)

someone who is in a situation where they are not really needed or are ignored by other people. I don't have a role in the office any more - I feel like a fifth wheel.

See also: fifth, wheel

the third degree (informal)

a situation in which someone tries to find out information by asking you a lot of questions. Where have I been, who have I been with! What's this? The third degree? If I'm even half an hour late she gives me the third degree. I got the third degree from my dad when I got in last night.

See also: degree