Here's what rhymes with lengthening.
                        
                        
                    
                                strengthening  restrengthening  Words that almost rhyme with lengthening
mentioning  pensioning  reckoning  lessening  reddening  leavening  threatening  editing  beckoning  deafening  leveling  deadening  freshening  reveling  reputing  questioning  settling  parenting  menacing  meddling  crediting  peddling  sectioning  entrancing  meriting  terracing  ferreting  pedaling  premising  seconding  beveling  caroling  deluging  bevelling  deputing  nettling  shellacking  necklacing  periling  tenanting  pebbling  kenneling  hennaing  trembling  sentencing  accrediting  heralding  resettling  headhunting  pencilling  processioning  developing  resembling  embarrassing  assembling  enveloping  unsettling  inheriting  unquestioning  breakfasting  nonthreatening  embezzling  imperiling  stencilling  disheveling  discrediting  credentialing  reassembling  redeveloping  subpenaing  disassembling  disinheriting  overdeveloping