Green’s Dictionary of Slang

a swindler who can be easily found out.

c.1698		B.E. Dict. Canting Crew.
1725		New Canting Dict.

an inadequate ruse, a plot that can be detected simply.

c.1698		B.E. Dict. Canting Crew n.p.: Cobweb-pretence, slight, trivial, weak.
1725		New Canting Dict.
1833		Morn. Chron. (London) 28 Feb. 2/5: Persons who ended their inflammatory and exaggerated addresses with a cobweb pretence of wishing for tranquility.

(UK Und.) a form of swindle or confidence trick.

1788

‘Rolling Blossom’ in Festival of Anacreon in Wardroper Lovers, Rakers and Rogues (1995) 180: The cobweb and the robbing rigs / I practise every day, sir.

an inferior, probably corrupt, gambling club.

1827

Guards 51: [T]he common hells, the rookeries and pigeon- holes, cobweb warehouses and fly-traps, where the Greek committee sits nightly.

(US campus) to have lived a celibate life for a long time.

1989

P. Munro Sl. U.