Abbreviation for the June 18th 1999 Carnival Against Capitalism, an event held simultaneously in over 80 countries.
London J18: protesters converged on the City of London and shut it down. McDonald's and some other places got a makeover Bakunin style, and other companies were forced to shut down. The cops turned up and started attacking people but were driven back repeatedly. The most successful anti-capitalist protest in Britain to date.
Nigeria J18 - probably the only one bigger than Britain. Workers invaded and tore down the offices of Shell in Nigeria, because shell are trashing the Niger Delta.
Eugene J18 - the biggest and most militant of the US events, featuring a street party which cops attacked, leading to some of the fiercest clashes anywhere. Persecution is also worst in America. One protester was victimised under the Three Strikes law and is still in jail.
Cologne J18 - pre-Seattle, and really the first of the big anti-summit protests - and the reason for all the rest. Protesters besieged the summit in Cologne and tried to get past security cordons.
Pakistan J18 - anti-nuke protesters got into a nuclear base and got arrested and told they would be charged with treason (but they weren't).
Not to be confused with C18 - although sections of the British press somehow managed this.
This was the first of a number of acronyms used for anti-capitalist protests, e.g. N20, S11, etc.