n. An insulting, emotional, caustic email message or newsgroup posting.
1999
Consumerama boasts that it's run by people 'with a *BEEF* & a WEBSITE!' An on-line forum for flames, bellyaches and the surrealistic Naked Mole-Rats of Marketing Award, it's fun to browse even if you don't have a gripe."
1996
Flames, also part of the Internet, are scathing messages whose vehemence is out of proportion to the perceived wrongdoing; they are usually unoriginal and poorly spelled. (Tip: Laugh and delete them.
1981 (earliest)
Sorry if the flame burns anyone, but I can't think of any other name for the unit that even comes close. Before Shannon no one understood how to factor in redundancy, etc.