“A weblog, also known as a *blog, is a frequently updated website consisting of dated entries arranged in reverse chronological order so that the reader sees the most recent post first. The style is typically personal and informal. Freely available tools on the World Wide Web make it easy for anybody to publish their own weblog, so there is a lot of variety in the quality, content and ambition of weblogs, and a weblog may have anywhere from a handful to tens of thousands of daily readers. Weblogs first appeared in the mid-nineties and became more widely popular as simple and free publishing tools such as Blogger.com became available towards the turn of the century….” Jill Walker
—Final Version of Weblog Definition (jill/txt)

Jill has responded to comments on the first draft. I quibbled with her use of “personal” and her focus on creative/diary weblogs rather than filter/community blogs, but her definition probably suits her intended audience (readers of an encyclopedia of narrative theory).