A metamorph was a designation of a lifeform that was able to shift, change or alter its appearance to take on the characteristics and appearance of another species (and then change back).
Examples of such beings include:
The ability of a metamorph could be achieved through technology as well. The Bane used Image translators to stay hidden. (SJA: Invasion of the Bane) During the morph process, morphic residue can be a byproduct, as was the case with the Bane and with the Vespiforms. (DW: The Unicorn and the Wasp)
One of the better known metamorphic species is the Zygons, who could use body-print technology to take the shape of humans. (DW: Terror of the Zygons)
The Abzorbaloff maybe a metamorph since he was able to disguise himself as a human
