If your website is registered with DMOZ (Open Directory Project), you may notice after altering your description tags, search engines such as Google still retain the description info from DMOZ instead.
The process of updating your DMOZ description may take a number of weeks, depending on the hectic schedule of the editors there. Placing the below code within your tags tells all search engines to ignore any DMOZ information regarding the page in question. After your site is next crawled, your description should be updated!
< meta name="robots" content="NOODP" />