shoot off one's mouth

vyjadřovat nepodložené názory, mluvit jako vševěd

It is never a good policy to shoot off one's mouth when knowing nothing of the facts. (Google)

Using such inelegant language is not nice for a public figure like him. To shoot off one's mouth and then apologize for it shows his crudity and insecurity. (Google)

The true mark of a person's maturity is not to shoot off one's mouth at something, but to understand and investigate it before stating your opinion. (Google)

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