The following is a list of English words without rhymes, called refractory rhymes—that is, a list of words in the English language which rhyme with no other English word. The word "rhyme" here is used in the strict sense, called a perfect rhyme, that the words are pronounced the same from the vowel of the main stressed syllable onwards. The list was compiled from the point of view of Received Pronunciation (with a few exceptions for General American), and may not work for other accents or dialects. Multiple-word rhymes (a phrase that rhymes with a word, known as a phrasal or mosaic rhyme), self-rhymes (adding a prefix to a word and counting it as a rhyme of itself), and identical rhymes (words that are identical in their stressed syllables, such as bay and obey) are often not counted as true rhymes and have not been considered. Only the list of one-syllable words can hope to be anything near complete; for polysyllabic words, rhymes are the exception rather than the rule.
Following the strict definition of rhyme, a perfect rhyme demands the exact match of all sounds from the last stressed vowel to the end of the word. Therefore, words with the stress far from the end are more likely to have no perfect rhymes. For instance, a perfect rhyme for discomBOBulate would have to rhyme three syllables, -OBulate. There are many words that match most of the sounds from the stressed vowel onwards and so are near rhymes, called slant rhymes. Ovulate, copulate, and populate, for example, vary only slightly in one consonant, and thus provide very usable rhymes for most situations in which a rhyme for discombobulate is desired. However, no other English word has exactly these three final syllables with this stress pattern. And since in most traditions the stressed syllable should not be identical—the consonant before the stressed vowel should be different—adding a prefix to a word, as be-elbow for elbow, does not create a perfect rhyme for it.
Words that rhyme in one accent or dialect may not rhyme in another. A commonplace example of this is the word of, which when stressed had no rhymes in British Received Pronunciation prior to the 19th century, but which rhymed with love in General American. (When unstressed, it's a homonym for have.) In the other direction, iron has no rhyme in General American, but many in RP. Words may also have more than one pronunciation, one with a rhyme, and one without!