Repeating synonym just once in title tag - is it keyword stuffing?

Hi all. I'm running a stock market forum and I noticed in Google Webmaster, I am not getting impressions for the keyword "message board." Currently, I only use the keyword "forum" in my title. For example, in Google Webmaster, I get impressions for "stock forum," but I don't get any impressions for "stock message board". I want to rank for "stock message board" as well. To fix this problem I am thinking of changing the title on my main homepage from:

"Stock Market Forum and Finance Discussion | AlphaBanter" to "Stock Market Forum and Finance Message Board | AlphaBanter"
(current example of the title of my homepage: Stock Market Forum and Finance Discussion | AlphaBanter)

And I am also thinking of changing the title on my sub-forums from:

"Facebook (FB) Stock Discussion Forum" to "Facebook (FB) Stock Discussion Forum and Message Board"
(current example of the title on my sub-forum: Facebook (FB) Stock Discussion Forum)

Some people say you shouldn't repeat the keyword more than once in your title. Is it safe to repeat the keyword a second time as a synonym? In this case, I am repeating the keyword "forum" with the synonym "message board" so hopefully Google will give me impressions for the keyword "message board" as well.