Honestly, Its use is similar to “fuck”, it’s informal in the speaken or the written, most used by teenager. It literally means “What a p*ssy look like”.
But in our daily conversation, it can be understood like “unbelievable” or “unpredictable” , for some following belows:
“vl” can mean “it’s so…, it’s very” like “ Nó đẹp vl luôn” => “It’s so fucking beautiful”
“mày ngu vl”, => “what a fool you are”
“Nó giỏi vl” => “He is so fucking good”.