A blog may be defined in this way:
“A Weblog is a Web site that maintains a constantly updated list of links to other sites; those links can deal with any subject or focus on a particular one. “
Another way to answer the request for definition of a blog is:
“A ‘blog’ is short form for ‘web log’, a sort of online personal diary. A blog lists posts ordered by date, in a personal journal format. Blogging just involves typing into a form and hitting the PUBLISH button.”
One more way one can state the definition of a blog is:
‘a type of website, usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in reverse-chronological order.’
Use whichever definition of a blog works for you.