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