Green’s Dictionary of Slang

1. unintelligible.

1693

Dryden Juvenal VI 99: For what so Nauseous and Affected too, As those that think they due Perfection want, Who have not learnt to Lisp the Grecian Cant?

2. pertaining to male prostitution (despite Greek adj. (2) context suggests as used by women).

1748

Spy on Mother Midnight II 4: I believe the Grecian Youths frequenting our Inns of Court, and the Coffee-Houses about Temple-Bar, may [...] raise a Party against Mother Midnight’s Verdict [on ideal penis size], which seems directly aim’d at the Deftruction of that tyrannical Dominion they have ufurp’d [...] meerly upon the Bulk, not the Strength, of their Parts.

3. cunning, sly .

1749

H. Fitzcotton (trans.) Homer’s Iliad 36: I only beg you’ll sell no brandy / To any Grecian Jack-a-dandy.

4. Irish, usu. of immigrants.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 91: Greek — Irishmen call themselves Greeks — none else follow the same track to the east; throughout this land, many unruly districts are termed Grecian.
1879		G.R. Sims Dagonet Ballads 118: There’s a thoroughfare fringing a Grecian abode.
1936		J. Curtis Gilt Kid 33: An Irish girl was sitting with two men. [...] He did not like these Grecian cows.

5. pertaining to (cheating) gambling .

1832

Satirist (London) 13 May 159/2: [T]heir [i.e. legitimate players] being generally as au fait at all the Grecian acquirements as themselves [i.e. cheats].