Green’s Dictionary of Slang

bleater n.1

[SE bleat]

1. (UK Und.) one who is tricked by a confidence trickster [‘a lamb (to the slaughter)’].

[UK]Dekker Lanthorne and Candle-Light Ch. 11: They that are Cheated by Jack in a Boxe, are called Bleaters.
[UK]B.E. Dict. Canting Crew.
[UK]A. Smith Lives of Most Notorious Highway-men, etc. (1926) 202: Bleaters, they that are cheated by Jack in a Box.
[UK]New Canting Dict.
[UK]Bailey Universal Etym. Eng. Dict.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.

2. a sheep or calf.

[UK]R. Brome Jovial Crew II i: Here’s Grunter and Bleater, with Tib-of-the-Buttry, / And Margery Prater, all dress’d without sluttry.
[UK]H.T. Potter New Dict. Cant (1795) n.p.: bleaters sheep.
[UK]G. Andrewes Dict. Sl. and Cant n.p.: bleaters lambs, sheep.
[UK]Flash Dict. [as cit. 1809].
[UK] ‘The Ship’s Butcher’ in Quid 203: The sheep he must attend [...] One by one the bleaters get the water.
[UK]G. Kent Modern Flash Dict. 6: Bleaters – lambs, sheep.
[UK]Flash Dict. in Sinks of London Laid Open [as cit. 1835].
Penrith Obs. 23 Dec. 5/4: The shepherd [...] was minus one of his choice bleaters.

3. a sheep-stealer.

[UK]G. Andrewes Dict. Sl. and Cant.
[UK]Flash Dict.
[UK]G. Kent Modern Flash Dict.
[UK]Flash Dict. in Sinks of London Laid Open [as cit. 1835].