Say a mouthful Definition 1 of 2Pro Tip 1/3Substantial Points Use 'say a mouthful' when agreeing with a strong point someone made. You said a mouthful there, the data does prove the theory. Pro Tip 2/3Casual Agreement It's often used to show casual but firm agreement in informal discussions. He's a tough opponent in debates—Jim truly said a mouthful. Pro Tip 3/3Not Literal The phrase isn't about speaking a lot, but about the weight of the words. When you pointed out the safety issues, you sure said a mouthful.