A serpent's tongue noun phrase
Soneone tends to speak in unkind and cruel way that is likely to upset or hurt someone else.
Many people doesn't want to make friends with Sue because she has a serpent's tongue.
The fossil tooth of a shark
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.'