Exactly like portmanteau, only much easier to remember. Two words are fused together by either joining a common syllable inbredneck or by compromising both (or possibly more) words to create an entirely new word with the combined meanings of both.
I called that rattle-trap pickup driver doing 45 in the fast lane next to an old lady that he was an inbredneck bastard for holding up traffic...of course I said it as I blew past him at 80 miles per hour.
Ex 2: "I heard a rawksome band at the club last night."
Both of these are examples of a frankenword.