Noun
near-Earth object (plural near-Earth objects)
(astronomy) A small Solar System body (ie. asteroid, comet, or large meteoroid) whose orbit brings it into proximity with Earth's orbit.
As per NASA’s Near-Earth Object Observations Programme, asteroids that are 140 metres or larger (bigger than a small football stadium) are of “the greatest concern” due to the level of devastation their impact is capable of causing. Source: Internet