"rat on" in Chinese (Simplified)
告发告密
Definition
向权威人士报告他人的不当行为或秘密，通常是背叛他人信任。
Usage Notes (Chinese (Simplified))
非正式表达，通常带有贬义，表示背叛（像“打小报告”）。常用于'rat on your friend'等句型，多指小事。正式举报严重犯罪不使用。
Examples
Don't rat on your brother to your parents.
不要向你父母**告发**你哥哥。
He promised not to rat on his classmates.
他答应不向老师**告密**同学们。
If you rat on me, I won't forgive you.
如果你**告发**我，我不会原谅你。
Nobody likes someone who always rats on their friends.
没有人喜欢总是**告密**朋友的人。
She didn't want to rat on her coworker, even though she knew he was wrong.
她不想**告发**同事，尽管她知道他做错了。
After he ratted on the group, no one trusted him anymore.
他**告发**了小组后，再也没有人信任他。