Hybridisation (hybridization)
Breeding between two distinct populations or species — the main threat to wildcats, because a wildcat that breeds with a domestic cat leaves offspring that are neither.
Where wild and domestic populations overlap, they interbreed. For European wildcats this is the central conservation problem: the threat is not only that wildcats are shot or run over, but that the surviving population slowly stops being genetically wild. A hybrid can look convincingly like a wildcat, which makes field surveys based on coat pattern alone unreliable.
The same word covers deliberate crosses in domestic animals, from wolf-dogs to cat breeds founded on a wild species. Those raise a separate set of questions about temperament and welfare, and several countries regulate how many generations must separate an animal from its wild ancestor before it counts as domestic.