Meteoroid has a specific scientific meaning. They can be rocks the size of a bus, down to tiny pebbles, or even ice chunks wandering through space under the influence of gravity. There is a constellation of unknown thousands of them in somewhat stable orbits around earth until they are disturbed by gravitational influences like our moon.

They only become meteors when they dive into our atmosphere and burn up. Only a rare few, based on their composition or size, make it all the way to the ground. Untold thousands of tons make it down in the form of dust motes.

The question is, could a large meteoroid one day strike earth and lead to the destruction of most or all life as we know it? 

15 minutes ago, Bill W said:

The question is, could a large meteoroid one day strike earth and lead to the destruction of most or all life as we know it? 

No. Meteoroids are much too small for that kind of destruction. An asteroid could do it, but they are exponentially bigger in scale. While a meteoroid may be big as a tractor-trailer rig, asteroids start out the size of a small city and go up. There has been some debate on whether to call the bigger ones asteroids or dwarf planets. The largest ones we know about have diameters of hundreds of kilometers.

1 minute ago, drpaladin said:

Yep. The last big meteorite exploded over Russia in 2013. It was between 17-20m in size and big for a meteoroid.

The Chelyabinsk meteor exploded with an estimated yield of 200 kilotons and did a considerable amount of damage and injuries on the ground.

The kind of damage a much larger one might do could be literally civilization ending.

This incident inspired NASA, the ESA and the Russians to keep a closer watch on the skies.