Definition of not know that in English:

not know that

phrase

informal
  • Used to express one's doubts about one's ability to do something.

    ‘I don't know that I can sum up my meaning on paper’
    • ‘I don't know that I can be any more specific than that because there are court proceedings pending.’
    • ‘I don't know that there's anything you can do; I think you've got to leave it up to him.’
    • ‘I don't know that I could go back to having a full-time job.’