Keyword stuffing
Keyword stuffing is considered to be a unethical Search engine optimization (SEO) technique. Keyword stuffing is when you load a Web page up with keywords in the Meta tags or on the Web page's content. The common techniques today for keyword stuffing are repeating the same word over and over again in the Meta tags, which is why many search engines don't look at the Meta tags anymore and also on the page with text that's the same color as the background, also known as invisible or hidden text.
The reason keyword stuffing is used is to obtain maximum search engine ranking and visibility for particular phrases with the purpose of getting visitors from the search engine (Such as Google, Yahoo!, etc.) to come to their web page. However, if the word is repeated to much it will raise a red flag to the search engines and they will likely place a Spam filter on the Web site or Web page.