According to Search Engine Watch, Google has changed the way it defines 'Doorway Pages'.
Doorway pages are typically large sets of poor-quality pages where each page is optimized for a specific keyword or phrase. In many cases, doorway pages are written to rank for a particular phrase and then funnel users to a single destination.
Whether deployed across many domains or established within one domain, doorway pages tend to frustrate users, and are in violation of our Webmaster guidelines.
Doorway pages are pages specifically made for search engines. Doorway pages contain many links – often several hundred – that are of little to no use to the visitor, and do not contain valuable content. HTML sitemaps are a valuable resource for your visitors, but ensure that these pages of links are easy for your visitors to navigate. If you have a number of links to include, consider organizing them into categories or into multiple pages. But in doing so, ensure that they are intended for visitors to navigate the sections of your site, and not simply for search engines.
In the new version of the definition, key sentences, words and adjectives have been changed and replaced by more generic terms. Discussions are on at the Search Engine Watch Forum. It seems that Google has tweaked the definition in order to make the look of the page more subtle than technical.