The Buddha spoke about the four kinds of wrong speech.
The first is lying
When a person goes to a court of justice, or in the company of relatives and friends, he would say ‘I know’ when he does not, and ‘I don’t know’ when he does. To save himself, or for the sake of some small gain, he deliberately utters lies.
The second is backbiting
When a person wanders here or there, he spreads falsehood around to cause disruption. He breaks up fellowship, does not reconcile those at strife, finds pleasure and delight in quarrels, and utters words to incite others to quarrel.
The third is harsh speech
The words spoken are insolent and rude, bitter for others to hear. People always accuse others, even for minor mistakes yet keep quiet when the latter do some good deeds. One writer says: ‘When I am good everybody forgets, but when I am bad everybody remembers.’
The fourth is idle babbling
This speech is made by a person speaking out of turn on things non-existent or irrelevant. His speech is unrestrained, out of place, thoughtless and does not bring any benefit whatsoever.
The next time before we speak, we must think before opening our mouths. The injunction ‘Think before you speak’ can help us avoid getting into disputes or arguments and avoid hurting others unnecessarily. We must analyze our thoughts and intentions before expressing them. We must not only know what to say, but also why, when, where and how to say it.
A wise man knows how to avoid problems by being careful about what he says. There is a saying that even a fish will not get caught on a hook if he knows how to keep his big mouth shut at the right time.
~ K. Sri Dhammananda, How to live without fear and worry