adj. 25B6; adjective
for some unaccountable reason : INEXPLICABLE, insoluble, incomprehensible, unfathomable, impenetrable, puzzling, perplexing, baffling, bewildering, mystifying, mysterious, inscrutable, peculiar, strange, queer, odd, obscure; informal weird, freaky; Brit. informal rum.
the Council is unaccountable to anyone : UNANSWERABLE, not liable; free, exempt, immune; unsupervised.