Not really a question but two words that don't rhyme with anything are purple and ironically poetry.
Ha! Good call. I think that we need to invent a word that can be used to define when a word doesn’t have a rhyme. I want to make up the word “smorange” just so we can knock orange out of the mix already. So, here is my dictionary entry….
Smorange: (n) A word that does not rhyme with another word in the English language, (ie. ‘Helicopter’, 'purple’, and 'poetry’.) Historically, the word 'orange’ was a smorange until of course the word 'smorange’ was invented.