insuperable
in.su.per.a.ble \(')in-'su:-p(*-)r*-b*l\ \-ble-\ aj [ME, fr. MF & L; MF,
fr. L insuperabilis, fr. in- + superare]to surmount, fr. super over - more
at OVER : incapable of being surmounted, overcome, or passed over -
in.su.per.a.bly av
Webster's English Dictionary