Overpopulation rhymes with:
population, population, manipulation, population, stipulation, accumulation, articulation, calculation, coagulation, confabulation, deregulation, emulation, formulation, granulation, innoculation, inoculation, manipulation, miscalculation, overregulation, ovulation, population, recalculation, regulation, reregulation, simulation, speculation, stimulation, stipulation, strangulation, tabulation, tribulation