Define Your Mum Straight Lol Meaning

Your Mum Straight Lol
One of the gayest insults on this planet out of all 69 planets there had to be this insult wtf

john: hey my homo brother nigga
Alex: nigga i white
John: your mum gay lol
Alex: (How did he counter my attack i must use the gayest insult to end his roasting career) YOUR MUM STRAIGHT LOL
John: oh ma dog man now i gotta comiict subasideeee
By Cassondra