Foolhardy (adjective)

1. Rash or reckless, especially in the face of danger.
2. Bold or daring in a reckless or foolish way.

Origin:

From fool + hardy, meaning rash or reckless, especially in the face of danger.

Examples:

1. It was foolhardy to attempt to climb the mountain in such bad weather.
2. His foolhardy behavior put his life in danger.
3. It was foolhardy to attempt to start the car with the gas tank empty.
4. His foolhardy decision led to his downfall.
5. It was a foolhardy to jump off the bridge without a safety harness.