User Activated Soft Fork, UASF

This definition comes from the technical glossary.

Definition

A Soft Fork activated by flag day or node enforcement instead of miner signalling.

Miner Activated Soft Fork (a soft fork activated through miner signalling)
Fork (a regular fork where all nodes follow the same consensus rules, so the fork is resolved once one chain has more proof of work than another)
Hard fork (a permanent divergence in the block chain caused by non-upgraded nodes not following new consensus rules)
Soft fork (a temporary divergence in the block chain caused by non-upgraded nodes not following new consensus rules)
Software fork (when one or more developers permanently develops a codebase separately from other developers)
Git fork (when one or more developers temporarily develops a codebase separately from other developers