If someone is described as having a sharp tongue it means they say things that are critical and harsh.
Don't worry about what the boss says, he has a sharp tongue.
Stephen's sharp tongue meant that nobody would ask him for advice.
If someone tells you to hold your tongue it means stop talking, particularly because they don't like what you are saying.
I'm always upsetting people at the meeting so next time I'm going to hold my tongue.
The photo shows an Indian man pushing a sword across his tongue in a ritual for Qudri Rafai Junoon Ali Sai, a local Sufi saint who died in 1971.