Using all letters

                                                                            discussion

                                                                           discussionis

                                                                            discussions

                                                                          The other words:

                                                                              coccus

                                                                              concuss

                                                                            concussion

                                                                            concussions

                                                                             conscious

                                                                               conus

                                                                             couscous

                                                                              cousin

                                                                              cousins

                                                                               cunni

                                                                              cuscus

                                                                              discus

                                                                              discuss

                                                                             disunion

                                                                               incus

                                                                             innocuous

                                                                             insidious

                                                                              nocuous

                                                                               nodus

                                                                             nonunion

                                                                             nonunions

                                                                               nouns

                                                                              nuncio

                                                                              nuncios

                                                                              odious

                                                                               scuds

                                                                              sinuous

                                                                               sinus

                                                                             sinusoid

                                                                             sinusoids

                                                                               sound

                                                                              sounds

                                                                            unconscious

                                                                               uncos

                                                                               undid

                                                                               union

                                                                              unions

                                                                              unison

                                                                              unisons

                                                                              unsound