Wound (adv) tight：If someone is wound tight or tightly wound, they are very tense and nervous or highly reactive. （弦崩得很紧，处于紧张状态、纠缠在一起）
You are very tense. Think of an old fashioned clock that you have to turn or “wind” to make the clock function. After turning the knob or “winding the clock”, the clock is now “wound”. The spring inside the lock is at it’s highest tension. If you wind it too tight, the spring (like a tight wound person) might snap.
E.G.1：I mean, how in the world could anybody accuse me of murder? Well, you are wound pretty tight. （DH S02E05）
E.G.2：So is, uh, Rex gone for good? — I don’t know. God, I hope not. I mean, they’ve always been wound a little tight, but I’ve never seen them like that. （DH S01E03）