Obviously, do what you can to avoid that situation. I've been writing software since the late 1970s and the times I've really, really had to fudge a reserved word is well under ten, probably closer to five.
There are lots of things you can do, such as doubling the first or last letter (reservedd) or adding a leading or trailing underscore (reserved_). What's appropriate will depend a lot on the conventions used language you're writing, especially with regard to leading or trailing underscores. Also try not to do things with case that could be misread by humans (e.g., using Reserved when it differs from reserved).
Once you've picked something, put it in your coding guidelines, make sure people know about it and that it's used consistently. I even go so far as to add a reminder comment so readers don't think it's a typo and know they'll be seeing it again:
int ccase; // Name dodges a reserved word