Cybrid was a name given to two distinct lifeforms modified off human templates, one involving Cyberman technology, and the other, quantum mnemnonics.
One of them referred to a human augmented with Cyber technology so as to emulate an android. They weren't "cyber-converted" in the usual sense of that word, but merely given some Cyber-technology to allow them to pass as androids. They were thus useful spies during the Orion War, a bitter conflict between humans and androids. (AUDIO: Keepsake)
The other referred to a lifeform created by Ashley Chapel by infusing a group of employees with a form of the power he'd been granted by the Saraquazel entity, transforming them into demonic dark-blue, clawed and horned entities. They also possessed fangs, and their skin was dotted with gold and silver markings resembling circuitry. They possessed a group mind and some semblance of their former selves, though they were brutal and required a controlling mind. In its absence, they yearned for one.
During the Great Kingdom crisis, a larger amount of Cybrids was created, enough to link the Tower of Abraxas (Canary Wharf, site of Ashley Chapel Logistics), the Ziggurat (the Millennium Hall, at the site of Battersea Power Station) and the Labyrinth (the Library of St John the Beheaded) in a chain. (PROSE: Millennial Rites)