Here's what rhymes with grammmatical.
grammatical ungrammatical Words that almost rhyme with grammmatical
radical national practical rational casual maximal mandible clavicle fallible palatal cannibal laughable passable cantonal chasuble cantabile satiable savable capital valuable compatible tangible diagonal irrational palpable taxable adaptable impassable impractical infallible pyramidal factional sagittal tractable flammable merchantable unpractical blamable impassible bankable fanciable invaluable transnational fractional implacable intangible intractable inflammable lnternational octagonal transactional impalpable verapamil retractable graspable nonflammable frangible attractable international incompatible multinational hexagonal interactional supranational detachable collapsible semiannual nontaxable unflappable declarable understandable expandable extrapyramidal nondetachable