silly sass

When you criticism someone in a way that isn't serious, you're being sarcastic. Especially when you make it really obvious to the person that you're just having some fun and don't mean what you say. Online, often emphasised with silly smilies and such!

'Oh look at them, lurking in the chat room, hiding from the rest of us!' :)

This is silly sass.
This is sissy sassing someone.