noun which may take the genitive case particle 'no', noun
unforeseen; unexpected; accidental
Used almost exclusively in fixed phrases like 不慮の事故 (unforeseen accident) or 不慮の死 (unexpected death). It describes events that happen suddenly and could not have been predicted or prevented.
彼は不慮の事故で亡くなった。
He died in an unforeseen accident.
不慮の災難に備えて保険に入る
I get insurance in case of unexpected misfortune.
A Sino-Japanese compound of 不 (not) and 慮 (thought, consideration), literally meaning 'without forethought' or 'unconsidered', which extended to 'unforeseen'.