flamenoun.
An insulting, emotional, caustic email message or newsgroup posting.
Example Citation:
"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."
Sam Vincent Meddis, "Space, colorful wonders and down-to-earth concerns," USA Today, September 15, 1999