Meaning:
“走” literally means to “go,” and “心” means “heart.” As “heart” here is related to “feelings,” this term, often used by Chinese netizens, means “thoughtful, deliberate.”
Example:
A: 昨天是什么特别的日子？为什么很多人在朋友圈秀收到的花？
Zuótiān shì shíme tèbié de rìzi？Wèishénme hěnduō rén zài péngyǒuquān xiù shōudào de huā？
Why was yesterday special? I found many people posting photos of the bouquets they received on WeChat Moments.
B: 你也太不走心了吧，难道你没给女朋友买礼物？昨天是5月20日，在中文里和“我爱您”读音相同。
Nǐ yě tài bù zǒuxīn le ba，nándào nǐ méi gěi nǚpéngyǒu mǎi lǐwù？Zuótiān shì wǔyuè èrshírì，zài zhōngwén lǐ hé “wǒ ài nín”dúyīn xiàngtóng。
How unthoughtful you were! Didn’t you buy your girlfriend a gift? Yesterday was May 20, which has the same pronunciation as “I love you” in Chinese.