According to Google Blogger….
“Blogs engaged in link spamming are called spam blogs, and can be recognized by their irrelevant, repetitive, or nonsensical text, along with a large number of links, usually all pointing to a single site.”
According to Wikpedia…
They are blogs “which the author uses to promote affiliated websites, to increase the search engine rankings of associated sites or to simply sell links/ads.”
According to wiseGEEK…
”A spam blog is a blog or website that exists for the sole purpose of receiving page visits and hits, usually through search engines. A spam blog is often referred to by the neologism "splog," which is a play on the words "spam" and "blog." Administrators who create spam blogs use a variety of tricks to achieve high search engine rankings and traffic.
Spam blogs often use blog scraping to increase the amount of relevant content visible to search engines. With blog scraping, the author copies an excerpt from another blog with or without a link back to the original post. The result is a blog post that appears relevant to a search engine and to a web user before he or she clicks on it, but the actual post contains little to no information. The term "splogging" refers to the act of creating a spam blog.”
