/ ˌʌnəˈkaʊntəbl; NAmE / adjective ( formal )
1.
impossible to understand or explain
SYN inexplicable :
For some unaccountable reason, the letter never arrived.
2.
unaccountable (to sb/sth) not having to explain or give reasons for your actions to anyone :
Too many government departments are unaccountable to the general public.
OPP accountable