Using term_description as keyword meta

I found a good use for WordPress’s taxonomy description. I’m using it to display keywords for the meta tag. When a user visits the archive page of a taxonomy the keyword meta will be displayed in the header.

Put the following code in your header file. Then make sure to put in a comma separated list of keywords in the description field of your custom taxonomy or category.

$desc = term_description( '', get_query_var( 'taxonomy' ) );

if($desc != '') echo '';

via Function Reference/term description « WordPress Codex.