Desync (IRC)
The state in which the servers of an IRC network no longer agree on what a channel looks like — who has ops, which modes and bans apply.
Every server keeps its own copy of each channel's state and relays changes along the spanning tree. When two changes cross in transit, or a server misses messages during a netsplit, the copies drift apart. A user could then be an operator as seen from one server and an ordinary member from another, and a ban might apply to half the network. In the channel it showed up as mode changes bouncing back and forth between servers with no human touching anything.
Desyncs were both a nuisance and a tool. Whoever ended up opped on the wrong side could use it before anyone reacted, which made them a staple of channel takeovers. The timestamps (TS) added to server protocols during the 1990s let servers decide which state was older and therefore authoritative, and the problem shrank from daily routine to trivia.