Here's what rhymes with callidissimus.
                        
                        
                    
                                grimace  Words that almost rhyme with callidissimus
vicious  bacillus  officious  cirrus  villus  limits  thickness  visits  fitness  sickness  pernicious  auspicious  citrus  fearless  viscous  assiduous  litmus  papyrus  thickets  dimness  hillocks  sinless  sinuous  nimbus  business  appearance  assistance  spirits  witness  bishops  adherence  ambitious  persistence  suspicious  delicious  digits  judicious  malicious  prodigious  richness  shipments  stiffness  stillness  tickets  diffidence  frigates  pickets  propitious  rivets  seditious  avaricious  bigness  billets  discus  pittance  pivots  repetitious  unfitness  bigots  pickups  riddance  snippets  wickets  witless  distance  religious  minutes  interference  assistants  clearance  exhibits  forgiveness  mistress  adherents  coherence  fictitious  inhibits  perseverance  superstitious  admittance  biscuits  capricious  hindrance  pigments  prestigious  prohibits  elicits  eyewitness  listless  quickness  swiftness  crickets  cystitis  factitious  injudicious  irreligious  resistless  beardless  hibiscus  litigious  mastitis  profitless  solicits  windlass  windless  wingless  existence  resistance  coefficients  commitments  disappearance  insistence  subsistence  brilliance  archbishops  meniscus  nutritious  reappearance  reminiscence  strictness  trinkets  consistence  eucalyptus  expeditious  indigence  remittance  surreptitious  transmittance  triplets  unambitious  unpropitious  adventitious  distinctness  incoherence  agribusiness  endearments  noninterference  coexistence  delinquents  contingents  infringements  nonexistence  enlistments  nonreligious