Meaning:

“太” means “very,” “可” is short for “可以,” which means “OK,” and “了” is an auxiliary word with no actual meaning. Roughly translated as “this is very OK with me,” the term is used by Chinese netizens to express a fondness for someone or something. The saying caught on after it was used during an episode of popular show “Rap of China,” and many people used it in bullet screen comments at Bilibili.

Example:

A: 听说你们换了班主任？

Tīngshuō nǐmen huàn le bānzhǔrèn？

People say you’ve got a new head teacher.

B: 是的，她是新来的英语老师，知识渊博、态度和蔼，人也长得美，太可了!

Shì de，tā shì xīnlái de yīngyǔ lǎoshī，zhīshí yuānbó、tàidù hé’ǎi ，rén yě zhǎng de měi，tàikěle!

Yeah, she’s our new English teacher. She’s knowledgeable, amicable and very good-looking. I’m a big fan!