chip on shoulder
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a chip on (one's) shoulder
An attitude that leads one to become combative or easily angered. Fred has such a chip on his shoulder—you never know what's going to set him off next. She won't admit it, but Kate has a chip on her shoulder when it comes to discussing her career.
*chip on one's shoulder
Fig. a bad attitude that tends to get someone easily upset. (*Typically: get ~; have ~; give one ~.) Why did you get so angry at the slightest criticism? You seem to have a chip on your shoulder.
chip on (one's) shoulder
A habitually hostile or combative attitude.