A brothel. The Floating Academy; the lighters on board of which those persons are confined, who by a late regulation are condemned to hard labour, instead of transportation.—Campbell’s Academy; the same, from a gentleman of that name, who had the contract for victualling the hulks or lighters.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
To sham Abram * Ace of SpadesNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes