Go into catalog > categories > list and click edit on a category. In the category info tab you will now find a checkbox option for "Include in top menu". Just uncheck this option for any category you do not want in the top menu. If you choose to have 0 categories in your top menu, it will use the default menu nopcommerce has had in the past. The only downfall at the moment, if you choose not to have categories in the top menu, when using responsive theme, there will not be a menu when viewing on a small phone. But there is a simple fix, just a little editing of the topmenu.cshtml which you can read about here: https://www.nopcommerce.com/boards/t/29579/responsive-menu-nop-330.aspx
Thank you for your reply. My problem is different than the one you mentioned. I want my category to be shown in the top menu. The problem with 3.3 responsive support is that along with the regular top menu entries, it has an extra list of categories listed one at a row underneath the correct top menu entries and within the top menu area.
I have to turn off responsive support to get around this problem. It has to do with my certain config, but I still cannot figure out what triggered it. It looks like a bug to me.