Here's what rhymes with lengthen.
                        
                        
                    
                                strengthen  Words that almost rhyme with lengthen
ensign  mention  tension  pension  gentian  attention  retention  ascension  dimension  invention  prevention  detention  dissension  pretension  declension  extension  convention  apprehension  contention  suspension  distension  reinvention  hypertension  reprehension  comprehension  condescension  misapprehension  incomprehension  lesson  lemon  lessen  reckon  resin  leaden  leaven  airman  lepton  redden  seven  engine  heaven  session  chairman  eleven  weapon  brethren  threaten  cession  freshman  headman  melon  felon  headmen  heron  pectin  beckon  chevron  deaden  freshen  penguin  destine  pennon  vegan  bellman  deafen  hessian  pressman  question  section  election  aggression  rebellion  oppression  erection  recession  tendon  dentin  pepsin  henchmen  sexton  henchman  hempen  penman  headsman  kelvin  direction  collection  depression  impression  possession  profession  selection  affection  correction  reception  rejection  accession  intestine  procession  regression  repression  suppression  digestion  obsession  resection  secession  ejection  ingestion  digression  stepson  selectman  refection  expression  connection  protection  exception  infection  intention  perception  reflection  suggestion  compression  detection  discretion  injection  objection  perfection  succession  concession  confession  connexion  progression  projection  redemption  resurrection  congestion  deception  deflection  dissection  inception  defection  inflection  dejection  reelection  preemption  redirection  reflexion  abjection  concretion  inflexion  bisection  repossession  indention  conception  inspection  recollection  complexion  exemption  insurrection  subjection  convection  intercession  distention  inattention  indigestion  abstention  indirection  watermelon  confection  reinfection  rhododendron  nonaggression  prepossession  subvention  intervention  intersection  imperfection  predilection  transgression  decompression  disaffection  indiscretion  dispossession  interception  retrogression  interjection  misdirection  delicatessen  genuflection  supervention  contraception  introspection  contravention  disinfection  disconnection  circumvention  preconception  retrospection  autosuggestion  misconception  interconnection  circumspection  nonintervention