Here's what rhymes with underdeclare.
                        
                        
                    
                                rare  declare  glare  lair  their  there  where  care  bear  fair  hair  share  chair  pair  prayer  wear  bare  dare  fare  tear  faire  hare  mare  ware  flare  mer  pear  flair  guerre  mehr  cher  fere  mair  pare  sehr  thair  blare  aware  square  affair  despair  repair  spare  swear  stare  beware  impair  scare  snare  stair  affaire  bugbear  curare  repairer  tinware  coheir  prepare  compare  unfair  forbear  disrepair  ensnare  midair  billionaire  parterre  dinnerware  beachwear  backstair  everywhere  anywhere  unaware  millionaire  underwear  earthenware  thoroughfare  doctrinaire  debonair  horsehair  solitaire  tableware  forswear  chinaware  maidenhair  outerwear  overbear  spyware  eldercare  ironware  legionnaire  millionnaire  broodmare  debonaire  funfair  camelhair  setsquare  silverware  aftercare  medicare  commissionaire  foursquare  kitchenware  foreswear  ovenware  wirehair  questionnaire  concessionaire  multimillionaire  extraordinaire  Words that almost rhyme with underdeclare
yell  well  cell  tell  fell  del  sell  bell  hell  shell  gel  tel  dell  delle  excel  nel  belle  celle  quell  weal  bel  knell  nell  quel  sel  telle  jell  smell  dwell  spell  swell  dispel  expel  repel  befell  cartel  gaol  gazelle  impel  lapel  resell  retell  morel  noel  parallel  hotel  compel  farewell  foretell  motel  nouvelle  propel  unwell  materiel  pastel  carousel  bagatelle  caravel  nacelle  novelle  carrousel  outsell  personnel  citadel  clientele  infidel  decibel  organelle  undersell  misspell  oversell  tagliatelle  mademoiselle  fontanelle  photocell  commonweal  nonparallel  muscatel  antipersonnel  zinfandel  therefor