Over at You Don't Say, John McIntyre points out that just because a word isn't in the dictionary doesn't mean it isn't a word:
But the point is not whether a dictionary has conferred legitimacy on either word; the point is whether the word is comprehensible and appropriate in context.
You and I can make up words. It’s easy. For example, you can attach the prefix anti- to just about any noun in English to create a word that will be immediately understood — even though it’s not in the dictionary. It will be a word.
The full post on the issue is well worth the read.