noun
putting on a brave face; pretending to be fine; bravado
Describes outwardly showing energy or cheerfulness while actually feeling down, anxious, or unwell. Often used when someone is trying to hide their true feelings.
彼は空元気で笑っていたけど、本当はとても悲しそうだった。
He was laughing with forced cheerfulness, but he actually looked very sad.
落ち込んでいるのに、みんなの前では空元気
Even though I'm feeling down, I end up putting on a brave face in front of everyone.
強がる is a verb meaning to act tough or pretend to be strong, often in a defensive way. 空元気 is a noun describing the outward display of energy or cheerfulness to hide negative feelings.
虚勢 is a more formal or literary term for bluff or bravado, emphasizing a show of strength or confidence that is not backed up. 空元気 is more about emotional pretense in everyday situations.
Compound of 空 (から, 'empty, hollow') and 元気 (げんき, 'energy, vitality'), literally 'empty energy'.