I don't know

idiom

Definition of I don't know

1 used to say that one does not have the information someone is asking for "What time does the library close?" "I don't know."
2 informal used to express disagreement, doubt, or uncertainty "I don't like that guy." "Oh, I don't know, he's not really so bad."She thinks we should go now, but I don't know. Maybe we should wait.