insurmountable
adjective formal uk/ˌɪn.səˈmaʊn.tə.bəl/ us/ˌɪn.sɚˈmaʊn.t̬ə.bəl/
（尤指问题或困难）难以克服的，不可逾越的
(especially of a problem or a difficulty) so great that it cannot be dealt with successfully
insurmountable difficulties 难以克服的困难
This small country is faced with an insurmountable debt. 这个小国面临着难以承受的巨额债务。