Poisonwords are words that may have a negative influence on your site. Those words or phrases can trigger suspicion or mistrust for websites and advertisements and may help identify your page as an unwanted page.  For example, a search engine may decide to rank sites using (too many) words relating to hatred lower, or Google Adsense Public Service Ads may  start showing up when you use death or natural disaster related terms on your page.See also: Adultwords or Stopwords.