Here's what rhymes with onceivably.
                        
                        
                    
                                conceivably  unbelievably  inconceivably  believably  irretrievably  Words that almost rhyme with onceivably
feasibly  peaceably  appreciably  inappreciably  indefeasibly  unrelievedly  unevenly  zealously  unspeakably  legally  speedily  agreeably  ceaselessly  fealty  grievously  serenely  heedlessly  naivety  seamlessly  sleepily  regally  cheekily  heedfully  sneakily  anemically  deity  secrecy  illegally  greedily  needlessly  regency  uneasily  unequally  dreamily  realty  genially  piquancy  drearily  obscenely  peony  phonemically  speciously  covetously  speechlessly  needfully  piquantly  sleeplessly  creakily  creepily  wheezily  squeakily  creamily  sleazily  frequency  frequently  recently  conveniently  decency  peacefully  supremely  decently  ingeniously  unfrequently  aridity  coherently  gleefully  ideality  leniency  facetiously  leniently  deceitfully  egregiously  irredeemably  breezily  congenially  greasily  queasily  coequally  infrequently  obesity  indecency  disagreeably  infrequency  indecently  dubiety  benignity  inconveniently  heterogeneously  homogeneity  spontaneity  centripetally  historicity  crystallinity  heterogeneity  simultaneity  contemporaneity