This article is from the Puzzles FAQ, by Chris Cole email@example.com and Matthew Daly firstname.lastname@example.org with numerous contributions by others.
What English words are hard to rhyme?
"Rhyme is the identity in sound of an accented vowel in a word...and
of all consonantal and vowel sounds following it; with a difference in
the sound of the consonant immediately preceding the accented vowel."
(From The Complete Rhyming Dictionary by Clement Wood). Appropriately
Wood says a couple of pages later, "If a poet commences, 'October is
the wildest month' he has estopped himself from any rhyme; since
"month" has no rhyme in English."
Unless noted otherwise, all words occur in Webster's Ninth Collegiate
Dictionary, Merriam-Webster, Springfield, MA, 1986.
NI3 = Merriam-Webster's Third New International Dictionary
NI2 = Merriam-Webster's New International Dictionary, Second Edition
RHD = Random House Unabridged Dictionary
+ means slang, foreign, obsolete, dialectical, etc.
Word Rhyme Assonance --------------- --------------------------------------- -------------------- aitch brache (NI2+), taich (NI2+) naish angry unangry (NI2+) aggry angst lanx beards weirds breadth death bulb pulp carpet charpit chimney timne, polymny (NI2+) cusp wusp (NI2) bust depth stepped eighth faith else belts exit direxit (RHD+) sexist fiends teinds, piends filched hilched (NI3+), milched (NI2) zilch filth spilth, tilth fifth drift film pilm (NI3+) kiln fluxed luxed (NI3+), muxed (NI3+) ducked glimpsed rinsed gospel hostile gulf pulse jinxed outminxed (?) blinked leashed niched, tweesht (NI2+) liquid wicked mollusk smallest mouthed southed month grumph mulcts bulks mulched gulched (NI3+) bulged ninth pint oblige bides oomph sumph (NI3+) orange sporange pint jint (NI2+) bind poem phloem, proem pregnant regnant purple curple (NI3+), hirple (NI3+) puss schuss rhythm smitham scalds balds, caulds (NI3+), faulds (NI3+) scarce clairce (NI2), hairse (NI2+) cares sculpts gulps silver chilver (NI3+) sixth kicks spirit squiret (NI2+) tenth nth bent tsetse baronetcy, intermezzi, theetsee tuft yuft twelfth health widow kiddo width bridge window indo, lindo wolf bulls