(simile) to talk like a book

(figuratively) to let guns do the talking; to settle the argument with guns

(informal, figuratively) to waste one's breath (to speak without being listened to) / (informal, figuratively) to blow smoke; to talk through one's hat (to speak about issues one doesn't understand)

(transitive with de) to talk through one's hat, to speak about an issue one doesn't understand

(literally) to speak too fast / (figuratively) to speak too soon

(transitive with de or que) to hear (of)

(informal) speak for yourself! (expressing disagreement with an opinion expressed by another)

extraparliamentary

freedom of speech

(figuratively) to speak to someone who doesn't listen; to preach to deaf ears