unaccountable
adj
1 that cannot be explained or accounted for 无法解释的; 难以说明的
an unaccountable increase in cot deaths, ie of babies 难以解释的婴儿猝死数量上升的现象
For some unaccountable reason, the letter never arrived. 不知何故, 那封信始终未收到.
2 ~ (to sb/sth) (fml 文) not answerable for one´s actions, etc; not accountable (对自己的行为等)不必负责任的, 无责任的.