Spamdexing (also known as search engine spam, search engine poisoning, black-hat search engine optimization, search spam or web spam) is the deliberate manipulation of search engine indexes. It involves a number of methods, such as link building and repeating related and/or unrelated phrases, to manipulate the relevance or prominence of resources indexed in a manner inconsistent with the purpose of the indexing system.
Spamdexing could be considered to be a part of search engine optimization, although there are many SEO methods that improve the quality and appearance of the content of web sites and serve content useful to many users.