Meaning:
Literally translated as “to exit a group chat,” this term originally refers to the scenario where a WeChat or QQ user “deletes and leaves” a group chat and therefore no longer receives new messages from that group. Chinese netizens jokingly use the term as a metaphor for “leaving a group” or “unwillingness to discuss a topic or participate in an activity.” Sometimes, people use the short form “退群” (tuìqún) to mean the same.
Example:
A: 美国总统特朗普最近在白宫新闻发布会上宣布，美国将退出世界卫生组织。
Měiguó zǒngtǒng tèlǎngpǔ zuìjìn zài báigōng xīnwén fābùhuì shàng xuānbù，měiguó jiāng tuìchū shìjiè wèishēng zǔzhī。
U.S. President Donald Trump recently announced at a White House press conference that the United States will withdraw from the WHO.
B: 感觉他担任总统之后就一直忙着退群。
Gǎnjué tā dānrèn zǒngtǒng zhīhòu jiù yīzhí mángzhe tuìqún。
It seems that Trump has been busy quitting various world organizations since he was inaugurated as president.