Using all letters

                                                                           muddleheaded

                                                                          The other words:

                                                                              allude

                                                                              alluded

                                                                               audad

                                                                              delude

                                                                              deluded

                                                                              dueled

                                                                              duelled

                                                                              dulled

                                                                              dumdum

                                                                               elude

                                                                              eluded

                                                                              hauled

                                                                              huddle

                                                                              huddled

                                                                              hulled

                                                                              hummed

                                                                               laude

                                                                              lauded

                                                                              lulled

                                                                              mauled

                                                                              medulla

                                                                             medullae

                                                                              mudded

                                                                              muddle

                                                                              muddled

                                                                               muled

                                                                               mulla

                                                                              mullah

                                                                              mulled

                                                                              mummed

                                                                              muumuu