Go into your search engine manager (via options or the omnibox's context menu) and edit the keywords for your chosen engine - note that we automatically add eng

Go into your search engine manager (via options or the omnibox's context menu) and edit the keywords for your chosen engine - note that we automatically add engines here with the keyword as the domain, so if you do a search on amazon.com, we'll automatically add amazon with the keyword 'amazon.com' - with autocomplete, this lets you type 'am', then press tab to search (or space-separate the keywork from the term).