say foolish things; make stupid comments
He was speaking nonsense about world economy. He knew nothing about it. He only talked through his hat.
29 be talking through your hat British English informal if someone is talking through their hat, they say stupid things about something that they do not understand
talk through your hat
to talk about something without understanding what you are talking about:
Nothing of what he said made sense - he was talking through his hat.
talk through one's hat in British
to talk foolishly
to deceive or bluff