Your suggestion of editing the article is completely workable and was working as per Wikipedia guidelines until Jayjg and SlimVirgin started deleting large relevant chunks of the article, and reverting it to what we have now, as punitive gestures.  If we can all agree to concentrate on making the article better, instead of punishing each other, there is no reason the article has to be locked.
I agree that we should start with an extremely innocuous definition preamble statement we can all agree on.  However, a definition doesn't do anyone any good unless it conveys some sort of information.  If there were just one word that we could all agree is associated with terrorism, that would be better than no definition at all: "intimidate" for instance.