The major search engines simply defined as those which are the most popular. To submit your site, click the "add url" link next to the search engine, and follow the instructions on that page. Bear in mind that search engines have different rules for how they index your site, and this may effect how you submit your site to them. To learn more about search engine submission, read our article "the art of submission".
Notes:
A pound sign next to the search engine name, indicates that you now have to pay for your site to be added to their database. It isn't possible to add to all search engines directly. For example, to get listed in Inktomi (without paying), you need to add your URL to one of it's partners such as Hotbot.
