noun, noun which may take the genitive case particle 'no'
unexpected; unforeseen; accidental
Used for events or situations that could not have been predicted, often with a negative connotation. Common in formal and written contexts, especially in phrases like 不測の事態 (unforeseen circumstances).
不測の事態に備えて、保険に入っておいたほうがいい。
You should get insurance in case of unforeseen circumstances.
彼の死はまったく不測
His death was a completely unexpected event.
Compound of 不 (fu, 'not') and 測 (soku, 'measure' or 'fathom'), literally 'cannot be measured/fathomed', hence 'unforeseeable'.