Someone called me on blocked number?

I have an iPhone 4s it came up "blocked" as where the name usually is then underneath it said unknown

What does this mean? Does it mean the person blocked my number?

I never blocked anyone

It means they used *67 to block there number so you don't see it. You were being pranked called.

No, it means the caller blocked their identity from you. It could have been a sales call from a company who use the number only for outgoing calls; some people prefer to have their number permanently blocked to prevent unwanted spam type mail coming through to their phone; or it could have been someone who specifically blocked this call to you personally to hide their identity from you on that occasion.

The caller's phone number appear as blocked if the caller chose to temporarily hide his phone number by entering a code before dialing your phone number.

With such calls, you can simply contact your telephone company and have them check on your account in their database. All the calls you make or receive are logged, with the other party's real information. So if you wish to know who's behind the calls or block them, you may request for it.