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