We don't use the word "reck" anymore, but to reck things meant to be thinking about them: to be careful about them, to be aware of them. We DO use the word "reckless," which means "NOT careful about things." If you're being reckless, you're acting in a fast, dangerous way, because you're NOT thinking carefully about what you should do or how you should stay safe.
This bus driver is reckless. He's driving recklessly: way too fast, and the bus is in danger of crashing. His reckless driving might injure or kill all of them.
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This diver is being reckless: chasing after a shark, trying to grab it. He could injure the shark. And, the shark could turn right around and bite him. Chasing after a wild animal is a reckless thing to do.
Remember: someone reckless isn't being careful or thoughtful, and doesn't care or think about the bad things that might happen because of what they do.
Idea 1: "It would be reckless to eat (some big amount) of (some delicious food), because (something bad or painful would happen)."
Idea 2: "Recklessly, (someone) (does something really wild and crazy), not thinking about how (something could get broken)."
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