A small piece of stone or piece of ore travelling through space, almost always in a solar system. Most are left over from asteroidal or cometary debris. Large meteors are rare.
Meteoroid: a tiny meteor. Despite their small size they are quite hazardous when impacting upon a fast-moving space craft
Atmospheric Meteor: a meteoroid that has entered a planetary atmosphere, usually making a fiery trail as it falls. All but the largest burn up before hitting the surface.
Meteor Shower: a phenomenon in which many meteors impact in a relatively short time and in approximately parallel trajectories. They occur when the planet passes through a comet or former comet's orbit, and is bombarded by left-over debris (rocks, etc.). Each meteor shower occurs at a predictable time each year. Showers are named after the constellation they seem to originate from (the radiant). Almost all meteor showers are harmless (contrary to some folklore and urban legends, the chance of being hit are exceedingly remote).
Meteor Storm: a very intense meteor shower.
Meteorite: a meteor that has impacted on a planetary surface.