I don't rightly know
I'm unsure about something; I don't have a response or suggestion right now. I don't rightly know what they're doing here—I didn't invite them, I swear! I don't rightly know what he was thinking when he made such a ridiculous statement.
I don't rightly know.
Rur. I do not know. Tom: When will Joe be getting back? Charlie: I don't rightly know. Jane: What's the difference between a first cousin and a first cousin once removed? Mary: I don't rightly know.