Read Titus 1:16 Using Other Translations
They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate.
They profess to know God, but they deny him by their works. They are detestable, disobedient, unfit for any good work.
Such people claim they know God, but they deny him by the way they live. They are detestable and disobedient, worthless for doing anything good.