Definition of "lurker"

It troubled me that there should have been a lurker on the stairs, on that night of all nights in the year, and I asked the watchman, on the chance of eliciting some hopeful explanation as I handed him a dram at the door, whether he had admitted at his gate any gentleman who had perceptibly been dining out?

1860 December – 1861 August, Charles Dickens, chapter XL, in Great Expectations […], volume III, London: Chapman and Hall, […], published October 1861, page 3

However, less than half of lurkers went online that often. Those who post also are more likely than lurkers to use the Internet for both work and pleasure. Posters use the Internet to communicate more with others than lurkers do.

2013, Richard Davis, Politics Online: Blogs, Chatrooms, and Discussion Groups in American Democracy, Routledge, page 92

In every large town sham official documents, with crests, seals, and signatures, can be got for half-a-crown. Armed with these, the patterer becomes a ‘lurker,’—that is, an impostor; his papers certify any and every ‘ill that flesh is heir to.’

1851, Henry Mayhew, London Labour and the London Poor; […], volume I (The London Street-folk. Book the First.), London: [George Woodfall], page 219