When reading Is a lightbox considered a dialog box? (and writing my answer) I realized our tag for "modal" stuff is modal-dialog. As you'll note in my answer, I don't agree that all modal things are dialogs; instead there are dialog (an existing tag) and there are modal-windows.
Modality is a different issue from dialog-ness. Dialogs can be non-modal, and not all modal interaction elements fit the classic "Alert: yes/no" format of the traditional dialog. In my opinion we should keep the ideas distinct and just tag dialog and modal-windows separately.