打小报告

打小报告

Literally means:

inform secretly on sb

Actually means:

rat on sb

It means making malicious remarks or talking against sb behind his or her back to his or her superior or senior, e. g. exaggerating or trumping up a weakness or charge.

The purpose of doing so is to downgrade other people, sometimes to show oneself or to win the trust of the superior or senior. Usually derogatory.

背地里向上级或长辈说某人的坏话（如夸大或捏造别人的缺点）。

目的通常是为了打击别人，有时还为了表现自己，或得到上级或长辈的信任。具有贬义色彩。