난공불락이에요 · 난공불락의 요새
impregnable, unconquerable
Example
그 성은 난공불락의 요새로 유명했어요.
That castle was famous as an impregnable fortress.
Word parts
난 difficult+공 attack+불 not+락 fall
Literally 'hard to attack, never falls.'
Good to know
Pronounced [난공불락]; also used for unbeatable champions or tough markets: 난공불락의 시장.