When we were up in North Dakota over Memorial Day weekend, my nephew, Jacoby, was just recovering from stitches in his forehead from a run in with a dresser. Considering how reckless fearless he is about climbing up on objects and running full speed everywhere he goes, the most common reaction was disbelief that this was the first time he had stitches. There were a few times over the weekend we would find him perched on top of something much higher than he should have been able to get onto by himself, and I would wonder how he got up there. And then I figured I really didn't want to know.
For the record, he climbed up on the carousel horse and the top of the slide by himself. I think fearless is a pretty good term.