Here's what rhymes with collectionism.
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mizzen mission rhythm arisen risen given addition vision commission edition listen permission physician prison admission ambition emission exhibition submission forgiven omission fission audition riven position condition definition driven recognition expedition petition suspicion coalition cognition collision exposition incision inhibition clinician ignition remission attrition derision fruition magician requisition sedition volition envision imprison intermission striven stiffen glisten decision division opposition tradition provision transition acquisition algorithm repetition supervision abolition ammunition intuition nutrition partition revision excision imposition musician supposition tuition admonition apparition circumcision erudition technician apposition contrition dentition extradition inquisition logarithm patrician redefinition rendition cataclysm logician premonition theoretician academician dietitian ebullition munition readmission rescission tactician competition composition television transmission disposition precision deposition politician prohibition superstition subdivision demolition mathematician indecision paroxysm precondition electrician manumission rhetorician imprecision prevision proposition preposition indisposition interposition superposition disquisition obstetrician statistician decomposition juxtaposition malnutrition predisposition transposition presupposition pediatrician superimposition diagnostician wisdom serum theorem cecum gingham system kingdom victim dictum gypsum fearsome winsome symptom pilgrim ecosystem