Overstatement rhymes with:
understatement, understatement, understatement, understatement, abatement, adjustment, allotment, apartment, appointment, assortment, commitment, compartment, comportment, contentment, department, deportment, disappointment, disenchantment, disinvestment, divestment, enactment, enchantment, enlistment, excitement, incitement, indictment, investment, maltreatment, misstatement, mistreatment, ointment, overallotment, presentment, readjustment, reappointment, recruitment, reenactment, reinstatement, reinvestment, resentment, restatement, statement, treatment, understatement
Overstatement sounds like:
overestimate, overestimated, overextend, overextended