Notes:

Like the TITLE code snippet, this does the same type of thing for the meta description. Again, edit the header.php to add this snippet below the title snippet, if you aren't using a plugin to manage this already.

<META NAME="description" CONTENT="<?php if ( is_single() ) {
            single_post_title('', true);
        } else {
            bloginfo('name'); echo " - "; bloginfo('description');
        }?>" />