'Worthless' in the Bible

Therefore, I tell you and insist on in the Lord not to live any longer like the gentiles live, thinking worthless thoughts.

Do not let unwholesome [foul, profane, worthless, vulgar] words ever come out of your mouth, but only such speech as is good for building up others, according to the need and the occasion, so that it will be a blessing to those who hear [you speak].