content delivery network.
So basically things like akamai have a global presence but direct users to local nodes for good performance.
Google dns can be a bit whacky e.g. sending eu users to america.
Opendns have worked with CDN providers to get good geo tracking and do have a UK dns server as well for that purpose.
Also opendns as a bonus do malware filtering as well if you want it.
I used to not like opendns as they use to breach rfc by redirecting failed lookups, but now they stopped that practice.