An absolute truth to everything around us.
What's the meaning of life?
I don't know, and I don't think anyone does.
A sex position in which the receiving party take a penis in every hole they have in their body
I asked her how she wanted to have sex and she said "I don't know" so I put it in everywhere including her ear and nose
I don't know=I have no knowledge of it or, I don't know how to answer that.
Person 1: How many muscles is in a cats ear?
Person 2: I don't know.
Person 1: Do you have summer plans?
Person 2: I don't know.