sylau can mean 2 things, 'shut yo lyin ass up' or 'shut yo lame ass up'. mosttly depends on the context tho
ex 1,
angel: bro this food so lame
vale: na bro sylau, this shit firee
ex 2,
vale: lol amongus hehe
angel: bro u ain funny, sylau
10๐ 2๐
So if someone is sayin sum lame ahh shi to you in text
Example:"books are good to read๐ค" then u say "sylau goofy ass bitch"