expression, noun which may take the genitive case particle 'no'
completely unconcerned; nonchalant; cool as a cucumber
Emphatic set phrase describing someone who remains utterly calm and unbothered, even in situations where others would worry. Often used with a nuance of mild criticism or admiration for someone's thick skin.
He's completely unfazed even when he fails.
That kid is totally unbothered even when scolded, and does the same thing again.