unaccountable

US /ˌʌn.əˈkaʊn.t̬ə.bəl/
UK /ˌʌn.əˈkaʊn.t̬ə.bəl/
1.

책임질 수 없는

not able to be explained or understood:

:
•
For some unaccountable reason, he forgot his car keys.