小报告 xiǎobàogào
[lodge a complaint against sb.with his superior;unhonest information made known to the superiors] 暗中收集情况向上级作的汇报。有时也称“小汇报”
不以光明正大的方式，私下向上级报告或反映。 如：「他最喜欢向老师打小报告。」