How do I set custom search engines in Android?

For years now, on every browser I own, Firefox, Opera, Chrome and Internet Explorer, I've assigned w as a shortcut/keyword to the custom search engine http://www.google.com/search?q=site:wikipedia.org+%s&btnI . That is, I just type w android comparison to jump to the befitting wikipedia article. I use many, many other custom searches. Is there a way to set this up on Android? Not necessarily with the stock browser?