Keywords embedded (usually invisibly) into a web page to attract search engines (spiders). The intended result of including spider food in one's web page is to insure that the page appears high on the list of matching entries to a search engine query. There are right and wrong ways to do this; the right way is a discreet ‘meta keywords’ tag, the wrong way is to embed many repeats of a keyword in comments (and many search engines now detect and ignore the latter).