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