UAHF
From CryptoWiki
User Activated Hard Fork.
Developers add a mandatory rule set to change the node software. These changes make previously invalid blocks become valid after a flag day, which do not require a majority of hash power to be enforced. Nodes with the rule set changes will follow this chain irrespective of its hash rate.
Was used to start up Bitcoin Cash by way of the UAHF Contingency Plan.
