What kind of expression is "Mouser in Chief"? How can I use this expression in the other way?
Native speaker’s answer
Rebecca
"Mouser in Chief" is a play on words based on the title "Commander in Chief", the person who has ultimate control over a military branch or armed forces. A "mouser" is an animal that catches mice, usually a cat. Therefore, the narrator calls the cat that lives at the British Prime Minister's house "Mouser in Chief" to be funny. This expression is not a part of standard English.