The adjective intrepid means someone who is extremely brave and willing to risk in dangerous situations.
Synonyms are courageous, fearless, heroic, or plucky.
The word origins from French (16th century) intrépide meaning “unmoved by danger, undaunted”, and directly from Latin intrepidus meaning “unshaken, undaunted, not alarmed”. It comes from in- meaning “not” plus trepidus meaning “alarmed”.
I joined a team of intrepid explorers.
The story shows how intrepid the firefighters are.
Mr. Wilson does not tolerate his intrepid students.