Here's what rhymes with authentical.
identical nonidentical Words that almost rhyme with authentical
helical heretical vesicle testicle vesical technical theoretical spherical lexical poetical metrical nonsensical hermetical electrical symmetrical unethical dialectical hysterical alphabetical asymmetrical antithetical arithmetical biomedical exegetical obstetrical parenthetical nontechnical angelical evangelical geometrical ecumenical imperceptible indelible academical unsymmetrical diametrical extendible nonelectrical pyrotechnical hemispherical petrochemical incomprehensible infinitesimal electrochemical trigonometrical