special combos in adv. melee?

I have a question. What is with these "special combos" in adv. melee?

A person will prepuch me and it will turn into adv. melee. I'll be getting most, if not all, the blocking correct but every once in a while, the attacker seems to be doing a special combo where he will get these 4-6 extra attacks in for free. When this happens it looks like the attacker is doing some spin attack around my guy and I cant block it.

I have never seen my character do this when I'm attacking in adv. melee. So is this some glitch or is this some special melee built in adv. melee? If so, how do you do it?

If you hit certain buttons in a special combination, there are two special combos to "unlock"...you get in 5 or 6 hits for free, and it can really help.
These aren't supposed to be given away, just learned. Try certain buttons, you'll find 'em out.

PS: One of the combos has one blue attack, the other is all green.

oh, ok. Thanks