The Open Directory Project (ODP) is a comprehensive human edited directory of the Web, compiled by a vast global community of volunteer editors. One source Google uses to generate snippets. You can direct Google not to use the ODP descriptions as a source by adding a meta tag to your pages.
The ODP is also known as DMOZ, an acronym for Directory Mozilla. The DMOZ name reflects its loose association with Netscape's Mozilla project, an Open Source browser initiative. The ODP was developed in the spirit of Open Source, where development and maintenance are done by net-citizens, and results are made freely available for all net-citizens.
<meta name="robots" content="NOODP">
To specifically prevent Google from using this information for a page's description, use:
<meta name="googlebot" content="NOODP">
If you use the robots meta tag for other directives, you can combine those. For instance:
<meta name="googlebot" content="NOODP, nofollow">