Radiant: Meteors actually pass through the atmosphere in near-parallel trajectories but appear to radiate from a point on the celestial sphere, called the radiant, in much the same way as the parallel lines of a railway track appear to converge to a point on the horizon.

Shower: Showers are usually named after the constellation in which their radiant appears. This is not always the case, however, because constellation boundaries have changed. The Quadrantids, for example, get their name from Quadrans Muralis, a constellation that no longer exists.

Duration: This is the period during which the shower is normally active. In reality, the start and end dates can change slightly.

Maximum: This is the date(s) of maximum activity. The Civil Calendar can cause the dates to change (e.g. because of leap days) and so astronomers prefer to use the position of the Sun, known as Solar Longitude. You have to be a real meteor geek to understand and convert Solar Longitude so we won't go into it here (and if you are a meteor geek you already know how to do it anyway).

R.A. (Right Ascension): The celestial equivalent of Longitude. It only matters to hardened meteor observers, so if you are a casual observer then don't worry about it.

Dec. (Declination): Latitude on the celestial sphere. See my comments on R.A.

Z.H.R. (Zenithal Hourly Rate): Are you paying attention? Good, 'coz this is where the science begins. The Zenithal Hourly Rate is the number of meteors you would expect to see at the time of maximum if the radiant was directly overhead and the observing conditions were perfect with a naked eye limiting magnitude of +6.5 - or at least that's the theory. In fact, even when these perfect conditions are met, the actual number of meteors an observer sees is usually at odds with the theoretical figure. So why do we use it? Beats me! Probably because everyone else uses it. If nothing else, it's a rough guide to how active a shower is. The higher the ZHR, the more chances you have of seeing a meteor.

Associated Comet: Meteoroid streams are really the debris left behind by the disintegration of a comet. Comets are usually named after their discoverer and can have up to three names (e.g. IRAS-Araki-Alcock). There are exceptions, such as Halley's comet (named after Edmond Halley who worked out when the comet would next be seen) and particularly bright comets that often attract the title of "The Great Comet of such-and-such a year." The Geminids appear to be associated with an asteroid or minor planet, but this may be a defunct comet that has lost all its icy/gaseous components.

Universal Time (U.T.): For our purposes, the same as Greenwich Mean Time (G.M.T.)

The International Astronomical Union's Commission 22 defined the terms to be used in meteoritics as long ago as 1961:

Meteor: The light phenomena which results from entry into the atmosphere of a particle from space. (Note it is only the light phenomena: not the sound or the actual body itself).

Meteoroid: Any object that moves in space and is larger than a molecule but smaller than an asteroid (say 1km).

Meteorite: A meteoroid which passes through the atmosphere (producing a meteor) and reaches the surface of the Earth without being completely vaporized.

Fireball: A meteor which is brighter than magnitude -4.0

Micrometeorite: A meteorite with a diameter of less than 1mm but greater than 1 micron.

Meteoritic Dust:  Very small particles less than micrometeorites.

Train: Anything left behind in the path of a meteor or fireball (e.g. ionization).

Wake: Very short train with a duration of less than 1 second.

Shower: A large number of meteors with nearly parallel trajectories.

Stream: A large group of meteoroids with nearly identical orbits.

Trajectory: The line of motion in three dimensions of a meteor in the atmosphere.

Path: The projection of the trajectory on the celestial sphere of the observer.

Bolide: The term bolide was not defined. Some people say a bolide is a particularly bright fireball, while others say it is an exploding or audible fireball. Until the IAU decides to define it the term should not be used. In fact, they are unlikely to do so. The late Peter Millman explained to me that if someone sees a fireball then that it how they will record it. But if another observer further down the track sees the fireball explode then they would record it as a bolide. So which is it? It can't be both: there wouldn't be any point in a "definition" in that case.

Meteor Stream: Meteor streams don't exist. Using the definitions given above, meteoroid streams exist and, if they encounter the Earth, they may produce a meteor shower, but clearly a "meteor stream" is nonsense!