Doing something dangerous and not worrying about the risks and the possible results. (Cambridge Dictionary)
Showing a lack of care about risks or danger, and acting without thinking about the results of your actions. (Cambridge Dictionary)
If you say that someone is reckless, you mean that they act in a way which shows that they do not care about danger or the effect their behaviour will have on other people. (Collins Dictionary)
Marked by lack of proper caution : careless of consequences. (Merriam – Webster)
Heedless of danger or the consequences of one’s actions; rash or impetuous. (Oxford Dictionaries)
Careless driving Vs reckless driving.
Are You a Risk-Taker or Just Reckless?