Be easily offended or quick to start a fight. 

(怒りっぽい)

A: "Why does John always seem so angry?" 

B: "I think he has a chip on his shoulder."

We use this phrase when we want to tell the listener that someone (including the speaker) is angry or seems angry. If referring to oneself, it’s fine to say, “I’ve got a chip on my shoulder about…(the problem)”