A plum in (one's) mouth British singular noun
Primally used in the UK to indicate the typical manner of communication from the high social class
Although she isn't from the high class, she can speak with a plum in his mouth, thanks to the careful teaching of his wise mother.
He always talks with a plum in his mouth, which makes people feel annoyed.
Used to describe someone who is good at persuading people to do or believe something
To argue with somebody
To say the same thing repeatedly
Ok, I get it! You sound like a broken record, seriously!