水军吐槽 is a segment in an internet forum ( http://bbs.thinkcmf.com/forum.php?mod=forumdisplay&fid=43 ), and it more or less translates to "ranting corner for keyboard warriors", although I think "ranting corner" would suffice (examples of similar segments on English forums: http://www.demons-online.com/archive/index.php/t-583.html , http://www.thethinkingatheist.com/forum/Thread-Ranting-corne... )

More on Chinese Internet Lingo:

http://www.douban.com/group/topic/20233083/
http://baike.baidu.com/view/3098178.htm