Several years ago a friend of mine and I were discussing words, and wondered whether there was a word that described a word which, when spelled backward, spelled another word. A palindrome, of course, is a special case of such a word, but we couldn't find a word to describe the general case of simply being a word when spelled backward. So we coined one - drow - but didn't at the time, and still don't, have the foggiest notion as to whether we re-invented the wheel or came up with an original. Does any wordsmith out there know whether there's already a word for such a word?

This was part of the AWAD email for Oct. 16, 2000:

"A special case of reversible words is palindromes, which spell the same when reversed. So palindromes are a subset of reversible words which in turn are a subset of anagrams. Another name for reversible words is semordnilap, a self-referential word coined by reversing the word palindromes."

Quinion!
http://www.quinion.com/words/weirdwords/ww-sem1.htm

(p.s. - Mrs. Bynre also records semordnilap for posterity.)

Dear drowser: I thought "retronym" might be what you are looking for, but it has been used in an entirely different way, meaning a new term to replace an old one.
Forthrighrist Phrontistery gives "ananym" for a name written backwards, which doesn't fit your search.

Maybe you could coin one, e.g. "reversonym" Surely you can improve on that.