Keyword
A word that is entered into the search form or search "window" of an Internet search engine to search the Web for pages or sites about or including the keyword and information related to it. In SEO the placement of keywords on web sites is a growing science to discover what sites come up first for specific keywords.

Keyword Phrase
General term used to define a specific word phrase that best describes the main topic of a web page. Synonymous with a search phrase that a visitor enters into a search engine to find specific information.

Keyword Stuffing
The act of repeating keywords or keyword phrases excessively in body copy, hidden text, meta tags, or any other code on the site. Originally done in order to increase rankings in search engines, this tactic is now recognized and penalized by most of the major search engines.