unlickable
adj/ʌnˈlɪkəbl̩/
Etymology From un- + lickable. By surface analysis, un- + lick + -able.
1
Incapable of, or unsuitable for, being licked.
2
Colloquial That cannot be defeated or overcome.
- We have tried to lick this problem although I think in a way it is unlickable through a variety of devices.1963, United States. Congress. Senate. Committee on Labor and Public Welfare. Subcommittee on Employment, Manpower, and Poverty, Nation's Manpower Revolution, volumes 7-9, page 2585: