noun which may take the genitive case particle 'no', noun
Describes someone who acts without fear, often to the point of being reckless. Can be used positively (fearless) or negatively (foolhardy) depending on context.
He is fearless and takes on any dangerous job.
若い頃は怖いもの知らずだったが、今は慎重になった。
I was reckless when I was young, but now I've become cautious.
Standard kanji spelling using もの in kana.
Variant with 物 for もの; less common but still seen.
Compound of 怖い (scary) + もの (thing) + 知らず (not knowing), literally 'not knowing scary things'. The exact historical derivation is uncertain, but the phrase has been used idiomatically to mean 'fearless' or 'reckless'.