1. John pushed his way in to the party and confronted Laura. He began to rant and rave and say things everyone knew he would later regret. He said a mouthful.
2. Everybody managed to keep the surprise party a secret until the last minute, when Jennifer’s younger sister gave it away. She said a mouthful before she remembered that the party was supposed to be a secret.

Compare to: go off half-cocked. The expression is usually used to describe when someone says a lot, not so much in terms of the number of words as in the significance of the words. 79