At work the other day, someone asked if there was a word for the style of menu that the latest versions Firefox and Microsoft Office now use; a single top level menu item which expands to a more familiar list of items and categories. "Top level menu" seems the most generic but doesn't explicitly refer to this style of menu.
Firefox has eliminated the "File, Edit, etc." menubar style completely and just has the single button to bring down the whole menu; Chrome does this as well with the little wrench icon. MS Office has hedged its bets and is using the familiar "File" heading but moved all items into one submenu (not counting the other tabs, those are actually part of the Ribbon). It's a style I've seen growing more popular to eliminate some of the chrome of the GUI but I don't know if it even has a formal/informal name.