This sneaky little armbar was done to us in training one day courtesy of Nuno Macedo :). This was one of those occasions that tapping was WORTH it.
This is an armbar you would get in side control when your opponent is framing against your hip. A pretty common action when being under sidemount,,, excellent >:)
Trap the Wrist.
Next, use your free arm to fold their legs to the mat.
Lastly, windhield wipe and throw your over his head and fall towards the legs.