Poison words, or forbidden words, is the name given to words or phrases that trigger suspicion, mistrust and loss of respect, or are of inappropriate character for a given web site in its consideration for a search engine. (according to wikipedia)
There is no list of such words. It will sometimes generate traffic to your website. But google sometimes does not advertise these, so better is to avoid them.
Poison words are such which can be cause for decrease page rank of our site. As such words like free , cheap , easy etc...we use either in keywords , title , url or anywhere else be negative impact for our site.
I never such word in my entire seo, but it sounded like words that's is not advantageous to your site or may do something blackhat. Anyways, I try to look for this poison and come back again if I have accurate information. I get confused about it.
I have only one idea . I think Duplicate content decrease your website ranking.
But here is not matter about duplicate content. Here its talk about poison word. And poison word harmful to your site and decrease your site ranking. And poison words which sometime use in keywords , title , or url also. And in search engine such words has pre-defined and site with those words consider as spam.