That depends on what you mean. Please keep in mind that Stack Exchange has a greater bent on individual post ownership than Wikipedia, so the golden rule of editing is "To clarify the meaning of a post (without changing that meaning)".
Editing a nondescript title into a descriptive one is permissible if you can interpret the question as a whole well enough to devise a title which reflects the probable intentions of the overall post. We may also incorporate information from the comments into an edit, if they accurately represent those intentions. Clarification of what was already expressed does require some amount of re-interpretation, so if you try to rewrite the title to better represent the probable intention so that people can understand the gist of the question better before clicking into it, then you should be fine. That makes it easier for people to find the question and know if they would be interested in viewing it.
However, if the post as a whole is so vague that you do not know what the question is probably meant to be, then you should probably leave the title alone, and vote to close the question instead. What we do not want to do is risk is a premature answer based on a misinterpretation of the questioner's intentions and have it rise to the top. If that happens, then it may garner premature votes and burden answers based on a correct understanding of the question with undue competition for the top voted answer. This is not only important because it helps find the questioner find the answer they seek more easily, but also because we want questions to serve all future visitors who find our website by making search engine queries which direct them to the question. Note that that the closure system is meant in part to compel questioners to make necessary edits that improve a post to the point where it can be practicably answerable and reopened. If clarification from the questioner is needed, and you can articulate what needs to be clarified, then please leave a comment explaining it, since that's part of why we have comments..
Basically, you should try to leave the question in a better state than you found it, but not at the risk of biasing the question by adding meaning to it that was never there in the first place.