Meaning:
“九” is short for “九年义务教育” (jiǔnián yìwù jiàoyù: nine-year compulsory education), and “漏鱼” is short for “漏网之鱼” (lòuwǎng zhīyú: a fish that escaped the net). This term, coined by Chinese netizens, literally refers to those who haven’t completed the nine-year compulsory education. It’s often used jokingly to mock those who are not well-educated and are found with spelling mistakes from time to time, especially those in showbiz.
Example:
A: 听说有一档选秀节目海选要笔试了。
Tīngshuō yǒu yīdàng xuǎnxiù jiēmù hǎixuǎn yào bǐshì le。
I’ve heard that a competition show will include a written test in the first round.
B: 真的吗？估计是要淘汰掉九漏鱼。
Zhēnde ma？Gūjì shì yào táotài diào jiǔlòuyú。
Really? I guess they want to weed out the poorly educated.