An outspoken dispute in a public forum such as a news group or email list, with usually about half a dozen fierce combatants.
Reason and logic seem to go out the door, and "ad hominem" attacks are plentiful. GodwinsLaw is sometimes (unwittingly) adhered to.
Note that a FlameWar, which is defined by the manner of discussion, is not the same as a ReligiousWar, which is defined by the topic of conversation. Naturally, though, they frequently overlap.
One 
famous flame war was opened by AndrewTanenbaum (a well-known ComputerScience professor who wrote many books about, among other topics, OperatingSystem design, as well as writing much of Minix) by a posting with the subject "LINUX is obsolete". See if you can spot any hostile language in this brief quote from Linus' first reply:
Re 2: your job is being a professor and researcher: That's one hell of a good excuse for some of the brain-damages of minix. I can only hope (and assume) that Amoeba doesn't suck like minix does.
http://www.flamewarforum.com/, a site decicated to FlameWars, where flaming is encouraged in the interest of passionate and entertaining debate.http://hates-software.com/, a mailing list dedicated to flaming hateful software4 pages link to FlameWar:
