空穴来风

Explanation: With the cave was into the wind. Dissemination of news and rumors analogy is not entirely without reason. Opportunity will also be used to spread rumors to. 　　Usage: The main predicate; as predicate, object, attribute; containing derogatory 　　Source: Chu Song Yu, "Wind Fu": "Chen Wen at the Teacher: 'Poncirus sentence to the nest, groundless'." 　　Examples: Boating Yaochuan swept temples, bamboo wind lamented. Although the order to become good care, but also ~ of righteousness. (Song Sun Guangxian "Bei" VII)