mouth of a sailor
mouth of a sailor
A tendency or proclivity to use coarse, rude, or vulgar language. I don't know what you're letting your son watch on television, but, for a fifth grader, he sure has the mouth of a sailor! My grandmother is the sweetest old lady you'll ever know, but, my lord, does she have the mouth of a sailor!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.