Here's what rhymes with thymergastic.
clastic mastic elastic plastic drastic monastic spastic fantastic scholastic dynastic inelastic sarcastic stochastic aplastic hyperplastic neoplastic gymnastic hypoplastic iconoclastic thermoplastic bombastic orgiastic periphrastic nonelastic enthusiastic ecclesiastic viscoelastic interscholastic unenthusiastic overenthusiastic Words that almost rhyme with thymergastic
gastric classic lactic tactic magmatic magic static fabric gigantic graphic panic frantic catholic erratic manic mechanic pneumatic synaptic galactic operatic phallic tannic slapstick malefic matchstick organic traffic romantic tragic hepatic metallic semantic ceramic climatic dogmatic emphatic schematic somatic thematic thoracic didactic ecstatic enigmatic hemorrhagic nomadic rheumatic asthmatic chromatic cinematic climactic fanatic pedantic thalamic achromatic haemorrhagic italic spermatic zygomatic acrobatic isobaric ataxic neoclassic tyrannic apparatchik baldric seismographic democratic dramatic dynamic automatic psychiatric aromatic inorganic pancreatic pragmatic traumatic volcanic autocratic enzymatic hydrostatic lymphatic metastatic oceanic sporadic aliphatic axiomatic cephalic galvanic glutamic kinematic messianic ophthalmic panoramic iconographic muriatic pelagic phlegmatic psychopathic satanic syllabic theocratic titanic bimetallic schismatic unromantic botanic intergalactic stigmatic sycophantic thermostatic phonographic unemphatic priapic aerobatic systematic aristocratic demographic geographic photographic symptomatic barbaric charismatic ethnographic pediatric prophylactic prostatic emblematic geriatric monochromatic nostalgic presynaptic prismatic programmatic psychosomatic topographic tympanic anaphylactic diaphragmatic heraldic holographic homeostatic idiomatic orthographic orthostatic splanchnic technocratic tomographic chiropractic oceanographic paediatric stenographic typographic astigmatic biographic calligraphic numismatic panchromatic undramatic photostatic xerographic diplomatic bureaucratic problematic asymptomatic cytoplasmic hypothalamic radiographic thermodynamic endoplasmic hemodynamic pornographic postsynaptic psychodynamic stratigraphic telegraphic angiographic diagrammatic intrahepatic lithographic monosyllabic undemocratic antidemocratic epigrammatic nonmetallic anticlimactic disyllabic meritocratic osteopathic plutocratic semiautomatic nondramatic homoeostatic idiosyncratic aerodynamic bibliographic chromatographic hydrodynamic melodramatic paradigmatic transatlantic cartographic intrathoracic posttraumatic unproblematic unsystematic cinematographic choreographic lexicographic nondemocratic polysyllabic undiplomatic unidiomatic electrostatic crystallographic protoplasmic autobiographic transoceanic electrocardiographic electroencephalographic