From Longman Dictionary of Contemporary Englishherculeanher‧cu‧le‧an /ˌhɜːkjʊˈliːən◂, hɜːˈkjuːliən $ -ɜːr-/ adjective BIGneeding great strength or determination a herculean task
Examples from the Corpus
herculean• To attempt such a thing would be herculean and quixotic.• This herculean task falls to the street environment services division of the Department of Public Works here.• This would appear to be a herculean task for the relatively efficient and an impossible one for everyone else.• The area will face a herculean task if it is to find a new occupier for that factory. 