JSONP

This suggests that you'd use the jsonp dataType (in a jQuery .ajax implementation) in lieu of the json dataType when reaching out to a web service that returns JSON at a different domain in a cross-origin attempt to drink data from afar.

It also suggests that jsonp "wraps the returned JSON data in a function call" apparently allowing for the cross-origin stuff to work instead of just blowing up as it would if merely json was used.