noun
lurker; read-only member
Internet slang for someone who only reads posts without contributing; often used in online forums and social media.
See also: ROM
彼は掲示板ではずっとROM専で、一度も書き込んだことがない。
He's always been a lurker on the bulletin board and has never posted even once.
ROM専の人も、たまにはコメントしてみてください。
Even if you're a lurker, please try commenting once in a while.