The idiom "have a chip on one's shoulder" means to be easily offended or to have a grudge against someone or something. It is used to describe someone who is always looking for a fight or argument, or someone who is always ready to take offense at the slightest provocation.
The origin of this idiom is not clear, but it is believed to have originated in the United States in the mid-19th century. It is said to have come from the practice of placing a wood chip on one's shoulder and daring someone to knock it off, as a way of provoking a fight.
In modern usage, the idiom is used to describe someone who is overly sensitive or defensive, and who is always looking for a reason to be angry or upset. It can also be used to describe someone who has a sense of entitlement or superiority, and who feels that they are owed something by others.
For example, if someone is always complaining about how they have been treated unfairly, or if they are always looking for a reason to argue or fight with others, you could say that they have a chip on their shoulder. Similarly, if someone is always bragging about their accomplishments and belittling others, you could say that they have a chip on their shoulder.
• Despite his success, he still has a chip on his shoulder from his difficult childhood. (present perfect, long-term attitude)
• I used to have a chip on my shoulder about my accent until I realized it's part of who I am. (past simple, personal experience)
• It's hard to have a conversation with her because she always has a chip on her shoulder and takes everything personally. (conditional perfect, hypothetical situation)
• I don't know why he always has a chip on his shoulder. (simple present, general statement)
• She's always looking for a fight, as if she has a chip on her shoulder. (present progressive, current behavior)
• He's had a chip on his shoulder ever since he lost his job. (past perfect, past event leading to current attitude)