unflappable

US /ʌnˈflæp.ə.bəl/
UK /ʌnˈflæp.ə.bəl/
1.

ไม่สะทกสะท้าน

not likely to get worried, nervous, or angry even in difficult situations:

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She's totally unflappable - you have to be when working in such a high-pressure environment.