used to refer to a person, thing, etc. when you do not know their name or when you are talking in a general way
Example:
- What would you say to Mrs So-and-so who has called to complain about a noisy neighbour?
a person who you find annoying or unpleasant. People sometimes say so-and-so to avoid using an offensive word.
Example:
- He's an ungrateful so-and-so.