ようがいけんご 要害堅固 LinksSentence search for 要害堅固Sentence search for ようがいけんごKanji details for 要, 害, 堅 and 固Edit in JMdict Noun, Noun which may take the genitive case particle 'no'1. (a fortress being) impregnable; unassailableYojijukugo (four character compound) Discussions Log in to talk about this word.