What is the meaning of this icon?

I changed the equipment of my character and this icon appeared

 

It means your armor lost it's durability. It will go from yellow to red, progressively.

The same thing will happen when your primary weapon loses durability, only it will show a sword icon.

If you look at the your paperdoll, the durability of your armor is probably zero. Time to repair it (I don't know if that's in game or not) or buy new stuff.

 

Currently the durability status doesn't mean anything. If durability hits zero, the armor is still providing full protection. Same with weapons. No need to run out and repair or get new ones, at least not yet.

 

Thank you!

 

Ahh man, I thought those were 'bonus' effectiveness icons, not penalties. :|