Cloaking is serving one thing to the search engine spiders and another to your human visitors. For example, the spider sees a highly SEO'd page with content galore and the visitor sees a squeeze page, or CPA landing page. Many fortunes were made with this method back in the day, but it is more difficult to do now. Google catches on pretty quickly now, but it is still possible to get away with it. Bumbersoft had a Wordpress Cloaker or wP Cloaker, but I don't know if they still support it (update the bots and user agents file). I still have some cloaked pages ranked with it though.