IPA: /ˈfɪr.ləs.li/
KK: /ˈfɪr.ləs.li/
In a way that shows no fear; bravely and confidently.
She fearlessly climbed the mountain despite the bad weather.
Fearlessly → It is formed from "fear" (from Old English "fǣr", meaning a feeling of anxiety or dread) and the suffix "-less" (meaning without) and the adverbial suffix "-ly" (meaning in a manner of). The word "fearlessly" means in a manner without fear or anxiety.
Think of being 'without' ('-less') 'fear' — that's why fearlessly means acting without fear.