That doesn't sound like one of the search plugins that normally ships with Firefox for Android. Could you check the following:

(1) Remove any unexpected / unwanted add-ons

menu > Tools > Add-ons

Or see: Find and install extensions on Firefox for Android

(2) Set default search engine

menu > Settings > Customize > Search

Note: menu paths based on Firefox 27

In case your search consists of only one word... This could be a redirect from your DNS service provider.

By default, any entry without spaces (e.g., my.web.site or intranet or omg) will be checked as a host name. Some DNS servers will honestly respond that no such host name was found, and Firefox redirects to a search engine. Some, however, report that it was found and show their own search results.

For this reason, you may get different results for 1-word searches on different networks (e.g., different wi-fi networks, different mobile networks).

I'm not aware of a way to shut off the DNS lookup, but other users have asked for that, so maybe if you search around you will see some suggestions. Feel free to check them with us first, in case they involve suspicious add-ons.

Try opting out at http://webhelper.centurylink.com/prefs.php