also: リードオンリーメンバ
noun
lurker; read-only member
Internet slang for someone who reads posts in an online community but rarely or never contributes. Often abbreviated as ROM.
wasei-eigo (Japanese-coined English), from read-only member
See also: ＲＯＭ
彼はリードオンリーメンバーで、書き込みはほとんどしない。
He's a lurker and hardly ever posts.
People who only read are sometimes called read-only members.