Something disguised to seem affiliated with a group OTHER THAN the one it really is affiliated with. For example, a "false flag operation" is a terrorist act committed by one group for the express purpose
of discrediting another group, which is framed
False flag operations in warfare are usually conducted at sea. They are generally speaking illegal, although there are loopholes. The object is to disguise one's own vessel as friendly to the enemy until it is possible to engage said enemy.
In 1980, right wing neo-fascists in Italy carried out a terrorist bombing of a waiting room in a Bologna train station. 85 people were killed. At the time, it was the deadliest terrorist attack in Europe since the end of the War.
At the time, it was blamed on Communists; and indeed, soon after, the PCI was badly beaten in parliamentary elections. In reality, it was a false flag operation carried out by fascists. Members of the notorious P2 Masonic Lodge
protected the identities of the perpetrators and later interfered with the investigation.