Hornet 是黄蜂、胡蜂或者马蜂。如果一个人不明智地捅马蜂窝，必然遭到大群马蜂的叮刺围攻。所以，stir up a hornet's nest的含义就是：捅了马蜂窝，惹人说辞或者招来批评的意思to provoke the attack of a swarm¹ of spiteful enemies or spirited critics。

例句：Why are you trying to stir up a hornet's nest? Our office has been managed this way for the last twenty years. Don't waste time complaining about it; you'll just get in a lot of trouble. 你为什么要去捅马蜂窝呢？我们的办公室这二十年来一向按照这个方式管理。你别浪费时间去提意见了；你会给自己招惹麻烦的。

又如：The case has stirred up a hornet's nest among the press and the congress. Everyone wants to know how this senior officer got away with stealing all those secrets for eight years before he got caught.  这件案子遭到新闻界和国会的强烈责难，使大家震惊的是这个高级官员怎么会窃取秘密情报长达八年之久才被发现。