In DC Comics, the term is used loosely in most instances to refer to any human-like individual with extraordinary, often paranormal abilities or other attributes, regardless of whether or not they are cosmic, mutant, scientific, supernatural, skill-based or technological in nature.
A significant portion of these are normal human beings born with a genetic variant called the "metagene",[1] which causes them to gain powers and other paranormal qualities during freak accidents or times of intense psychological distress, effectively making them a subspecies of superhumans living within the population.
The term was first used as a reference to superheroes in 1986 by author George R. R. Martin, first in the Superworld role playing system, and then later in his Wild Cards series of novels.
The prefix meta-, in this context, simply means "beyond"—as in metastable, which is beyond regular stability and ready to collapse at the slightest disruption, or metamorphosis, which is the state of going beyond a single shape.
During the Final Crisis, while the Dominators devised a Gene Bomb able to accelerate the metagene activity to the point of cellular and physical instabilities, an anti-metagene virus was spread as a last-ditch weapon in the invaded Checkmate quarters.
This metavirus has the opposite effects of the Gene Bomb, curbing and shutting down the metagene and stripping the metahumans of their powers for an unspecified amount of time.
Whereas before, evolution would have eventually made mankind into a race of superhumans similar to the Daxamites and Kryptonians, now only a select few humans would develop metahuman powers.
According to Countdown to Infinite Crisis, roughly 1.3 million metahumans live on Earth, 99.5% of whom are considered "nuisance-level" (such as kids who can bend spoons with their minds and the old lady "who keeps hitting at Powerball").
The first use of the term 'metahuman' in the Marvel Universe occurred in New Mutants Annual #3, written by Chris Claremont, published in 1987, in which a Russian security officer describes the protagonists as "metahuman terrorists".
However, the majority are the result of exposure to kryptonite, which in the Smallville universe can turn people into superpowered "meteor freaks", often with psychotic side effects.
For many seasons of Smallville, all superpowered people other than Kryptonians were so-called meteor freaks, but as the show went on, it began to explore further corners of the DC Universe.
On the animated series Young Justice, the aliens known as the Kroloteans have frequently used the term and have even researched into the discovery of a "metagene" by abducting and testing on random humans.
The alien Reach conduct similar experiments and kidnap a cadre of teen runaways to test for the metagene, leading several of these individuals to develop superpowers.
Labs scientist surmises that the gene is "opportunistic" in as much as it causes its user to develop powers seemingly based on their personal experiences or surrounding depending on circumstances.
In the Arrowverse family of live-action shows, "metahuman" is used more narrowly than in the comics, typically referring to a human being who becomes transhuman and has uncanny abilities, often acquired following some kind of strange accident.
In the television series Gotham, Professor Hugo Strange experiments with dead (and alive) bodies of criminals, Arkham Asylum patients, and civilians under the orders of the Court of Owls.