Octogenarian rhymes with:
disciplinarian, centenarian, disciplinarian, planarian, seminarian, septuagenarian, veterinarian, wagnerian, aerien, agrarian, authoritarian, bagdasarian, barbarian, bavarian, berrian, berrien, bilzerian, bulgarian, carrian, carrion, centenarian, clarion, contrarian, darien, disciplinarian, egalitarian, eskandarian, humanitarian, hungarian, kasparian, kazarian, kerien, lauretarian, libertarian, librarian, magarian, majoritarian, marian, marion, markarian, merion, najarian, nazarian, nonsectarian, ovarian, parliamentarian, planarian, proletarian, sectarian, seminarian, septuagenarian, skenderian, terrien, totalitarian, unitarian, utilitarian, varian, vegetarian, veterinarian, wagnerian, zakarian