Meaning:

“赢” means “to win,” “麻” means “numb,” and “了” is an auxiliary word implying a perfect tense. This recently invented phrase, frequently used by Chinese netizens, means that because someone or something has won very big or many times, they become numb to their success. Depending on the context, this phrase can be used sincerely, or sarcastically as when the speaker implies a person is just intoxicated by their illusion that they are invincible.

Example:

A: 你弟弟最近炒股赚钱了吗？

Nǐ dìdì zuìjìn chǎogǔ zhuànqián le ma？

Did your younger brother make money from his recent investment in stocks?

B: 他赶上了智能聊天机器人相关概念的炒作，赢麻了。

Tā gǎnshàng le zhìnéng liáotiān jīqìrén xiàngguān gàiniàn de chǎozuò，yíng má le。

He jumped on the bandwagon of the fever for AI chatbot companies and won big.