noun, noun which may take the genitive case particle 'no'
Describes a person or attitude that shows no fear; often used in a positive, admiring sense.
彼は恐れ知らずの冒険家だ。
He is a fearless adventurer.
その選手は恐れ知らずのプレーを見せた。
The player showed fearless play.
大胆 means 'bold' or 'daring' and can imply recklessness, while 恐れ知らず focuses on the absence of fear itself.
不敵 also means 'fearless' but often carries a nuance of defiance or audacity, sometimes negative.
Compound of 恐れ (fear) and 知らず (not knowing), literally 'not knowing fear'.