From Bulbapedia, the community-driven Pokémon encyclopedia.
The Meteonite (Japanese: メテオナイト Meteonite) is an item that appeared in the Best Wishes series. It was the central focus of Team Rocket's mission from In The Shadow of Zekrom! to Battling For The Love of Bug-Types!.
In Triple Leaders, Team Threats!, Jessie, James and Meowth were assigned to collect energy from the Dreamyard, a mission they carried out in the next episode. Giovanni revealed that he would use the energy to search for a similar signature and would contact them with more information soon.
Giovanni directly introduced Jessie, James and Meowth to the Meteonite in his briefing to them in The Bloom Is On Axew!. He explained that in ancient times, a giant Meteonite entered the Earth's atmosphere and broke apart, making impact in pieces throughout the world with the largest piece being somewhere in Unova. Further explaining that the Meteonite, even in small pieces, could conduct massive amounts of energy, such as the energy from the Dreamyard, Giovanni assigned the trio to seek it out, as he intended to use it to further Team Rocket's plan for world conquest.
In A Home For Dwebble!, Pierce assigned the trio to break into a facility known as the Antimony Research Lab to steal data on the Meteonite. Using a series of devices, they successfully downloaded the research data. Later, in Here Comes The Trubbish Squad!, a Team Rocket agent delivered a fake Meteonite to the trio, with instructions to wait for further orders. After confirming they had the dummy Meteonite in A Night in the Nacrene City Museum!, Pierce assigned the trio to break into the museum to switch it with a small piece of the Meteonite, which they did in The Battle According to Lenora!.
Dr. Zager arrived to examine the piece of the Meteonite in Scraggy—Hatched to be Wild!. He discovered that, as he suspected, it was comprised of elements not found on the planet. When it reacted to the beam of Dreamyard energy he was examining it with, he excitedly declared that it was what he was looking for.
In A Venipede Stampede!, Jessie, James, Meowth, Pierce and Dr. Zager flew over the Desert Resort, using the small Meteonite to scan for the larger one. When they discovered it, the energy pulses in the nearby area destabilized, a swarm of Venipede fled the desert and descended upon Castelia City. Giovanni was later seen heading for Unova in order to oversee its collection in person. At the end of the episode, Professor Juniper went to the desert to investigate what had happened.
Two unaired episodes were to have featured the climax of Team Rocket's quest for the Meteonite and their fight with Team Plasma over it, until they were indefinitely postponed and later retconned out of continuity. A preview for the episodes, however, gave away in it's conclusion that the Meteonite was to be ultimately destroyed by Pikachu, had the episodes still be a part of canon. In Battling For The Love of Bug-Types!, Matori told Jessie, James and Meowth the mission was over and discharged them to do as they pleased in Unova. It is unknown as of the retcon what happened to the Meteonite at this point, thoigh it still maybe in Relic Castle.