What does "unidentified" mean on cell phone caller ID?

Question

I know what restricted means - the person has blocked caller ID, whether *87 or the service.

But today I missed a call labeled "unidentified". What does that mean?

Thank you for any information!

Answer 1

means somebody was trying to prank call u, or they did not fill in their information

Answer 2

it means its a private call

Answer 3

hmm, never heard of that. it may have been out of your service area so it couldn't send the full information. thats my guess.