空谷足音

空谷足音：kōnggǔzúyīn基本解释：[thesoundoffootstepsinadesertedvalley-anewsorastatementwhichonedoesnothearoften,orathingthatwasseldomtofound]空旷的山谷里听到的人的脚步声。比喻十分难...