Currently we offer no search in Wikipedia that returns search results in any language. www.wikipedia.org is our international entry page and this page would be the ideal place to add a search option "in any language".
Implementation idea: Such a search could be simply implemented by using Google to do a full text search on the domain wikipedia.org. For example, this would be the result of a search for "Enterobius vermicularis": https://www.google.de/?gws_rd=ssl#safe=off&q=%22Enterobius+vermicularis%22+site:wikipedia.org (If we can implement such a search without Google, then all the better.)
See Also:
T26767: Multilingual search on project portals (e.g. www.wikipedia.org)