IPA: //ʌnˈflæp.ə.bəl//
KK: /ʌnˈflæp.ə.bəl/
Someone who remains calm and composed in difficult situations and does not get easily upset or excited.
Even during the crisis, she remained unflappable and handled everything with grace.
Unflappable → It is formed from "un-" (meaning not) and "flappable" (from the verb "flap", meaning to move or wave quickly). The word describes someone who is not easily moved or disturbed, remaining calm under pressure.
Think of someone who is 'not' ('un-') easily 'moved' or 'disturbed' ('flap') — that's why unflappable means remaining calm in stressful situations.