Answer: lurker

AnswerCrossword Clue
LURKEROne who skulks
lurkerone who lurks (to lie in wait)
lurkerto lie hidden
LURKEROne who reads but doesn't contribute
LURKERHe's sneaky
LURKEROne who prowls
LURKERSkulker
LURKERChat room nonparticipant
LURKERFurtive sort
LURKERPassive reader on line
LURKERSneak
LURKERProwler.
LURKERChat-room nonparticipant
LURKERShadowy
LURKERPerson who reads online but doesn't comment
LURKERShy chat room participant
LURKEROnline newsgroup non-participant