三寸不烂之舌

sān cùn bù làn zhī shé

to have a silver tongue

to have the gift of the gab

三

sān

three

寸

cùn

a unit of length

不

bù

no; not so

烂

làn

soft; mushy

之

zhī

(possessive particle, literary equivalent of 的[de5])

舌

shé

tongue