One who lurks. / (Internet slang) A user who observes a community rather than participating; someone who reads or takes advantage of content on a website, newsgroup, etc. but does not contribute.

plural of lurker

(uncountable, Internet) The state or quality of being a lurker. / (countable, Internet) The lurkers who frequent a newsgroup, message board, etc., taken as a group.

plural of lurkership