Home / HSK Vocabulary / HSK 7–9 / 牢固 牢固 láo gù HSK 7–9 · C2 Meanings firm secure Quick facts HSK LevelHSK 7–9 CEFRC2 ← Back to HSK 7–9 word list Practice 牢固 with flashcards MandoBridge uses spaced repetition to help you remember HSK 7–9 vocabulary — free on iOS and Android.