When a girl text you. "Mmmk" "k" or "K." you really fucked up like you owe this girl flowers and chocolate. And you need to kiss her feet. You made her super upset
A phase used to reply to something. Usually indicates nothing, just a reply to fill in the silence. It's not negative, nor a positive reply. It is barely used to indicate awkwardness on a conversation. Sometimes ended with ok/okay.