Using all letters

                                                                           substitutive

                                                                          The other words:

                                                                              bubbies

                                                                              busbies

                                                                               buses

                                                                              busies

                                                                              busiest

                                                                              busses

                                                                             bustiest

                                                                               busts

                                                                               butte

                                                                              buttes

                                                                               butts

                                                                               issue

                                                                              issues

                                                                               situs

                                                                             stubbiest

                                                                               stubs

                                                                              subset

                                                                              subsets

                                                                              subsist

                                                                             subsists

                                                                            substitute

                                                                            substitutes

                                                                               suets

                                                                               suite

                                                                              suites

                                                                               suits

                                                                              suttee

                                                                              suttees

                                                                              tissue

                                                                              tissues

                                                                             tubbiest

                                                                               tubes

                                                                               tutee

                                                                              tutees

                                                                               tutti

                                                                               tutus

                                                                             vesuvius