1. Soneone tends to speak in unkind and cruel way that is likely to upset or hurt someone else.
2. The fossil tooth of a shark
1. Many people doesn't want to make friends with Sue because she has a serpent's tongue.
2. A: 'My thesis will center on a serpent's tongue.' B: 'A serpent's tongue? What does it mean?' A: 'A serpent's tongue means the fossil tooth of a shark.'