Opposition procedure before the European Patent Office
The opposition procedure before the European Patent Office (EPO) is a post-grant, contentious, inter partes, administrative procedure intended to allow any European patent to be centrally opposed. European patents granted by the EPO under the European Patent Convention (EPC) may be opposed by any person from the public (no commercial or other interest whatsoever need be shown).
Source: Wikipedia — Opposition procedure before the European Patent Office (CC BY-SA 4.0)