serengeti - 1:18 am on Nov 18, 2009 (gmt 0)

I own a website with phpbb forums attached to it.

I have 5-10 keywords related to my topic that I would like my site ranked for (even if the ranking is outside the top 50 or so). Some of those keywords are virtually synonyms for each other.

Unfortunately, google has 4 of my site's top 5 most popular keywords listed as "post" posts" "forum" and "topic", because those words keep increasing in frequency every time someone makes a post on the phpbb forum.

How do I prevent google from counting those keywords?