"rat on" in Chinese (Traditional)
告密告發
Definition
向權威人士舉報他人的錯誤行為或祕密，通常是在背叛信任。
Usage Notes (Chinese (Traditional))
非正式用語，通常帶有貶義，指背叛（如“打小報告”）。常見於如 'rat on your friend'，多指瑣事，正式檢舉嚴重犯罪不常用。
Examples
Don't rat on your brother to your parents.
不要向你父母**告密**你哥哥。
He promised not to rat on his classmates.
他答應不向老師**告密**同學們。
If you rat on me, I won't forgive you.
如果你**告密**我，我不會原諒你。
Nobody likes someone who always rats on their friends.
沒有人喜歡總是**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**告密**同事，雖然她知道他做錯了。
After he ratted on the group, no one trusted him anymore.
他**告密**了團體後，再也沒有人信任他。