Actually, I'm claiming that you could make yourself not ignorant in less time than it took you to write your last post. I'm pleading with you to do so. But, here, I'll help you along since you apparently have an aversion to search engines:
Here's an explanation of reductio ad absurdum: http://www.iep.utm.edu/reductio/
Here's an article with a list of 208 fallacies, which you should note does not contain reductio ad absurdum: http://www.iep.utm.edu/fallacy/
It's good reading for everyone, but I particularly recommend it to you. If you want more sources, do some simple searches and you'll find more than anyone has time to read. But, even consulting, say, the first page of results, you'll find that reductio ad absurdum is a valid method of argument, not a fallacy.