To seize something is to grab it strongly or quickly, or to take it away from someone with force and power. A seizure is a fast or dramatic grabbing. Seizures aren't gentle or slow.
For example, you would seize your little sister if she were about to run out into the road: you would quickly grab her, to keep her safe from the cars. Or, you might seize her wrist to stop her from grabbing onto a hot pan. Here's Moana seizing Maui by his ear. Ouch!
Police might seize criminals: grab onto them and stop them from escaping. Or, police might seize illegal drugs from criminals: that means they have the authority to take their drugs away.
So far, we've talked about people or animals seizing objects or other people. Let's also get abstract! When you feel as though a fear or a worry is grabbing onto you, you might say that this fear or worry has seized you. Or, when an idea or a dream has grabbed onto you, or grabbed onto your mind or your heart or your imagination, you might say that the idea or the dream has seized you.
You can also seize control of a situation, meaning you find a way to quickly take control of it. You can seize a chance or an opportunity, meaning you take it, as if you're grabbing onto it and holding it tightly. And, you can seize the moment, or seize the day, which means you take bold, strong action right away, as if you're grabbing onto the moment or the day and making the most of it.
Finally, if something seizes up, like a motor or a computer, that means it gets stuck or it stops working properly, as if something has grabbed it. And if a person seizes, or if a person has a seizure, they're having a sudden electrical disturbance in the brain that affects how they're able to move or think. Again, it's as if something is suddenly grabbing onto them.
