Green’s Dictionary of Slang

grift n.

[graft n.1 ]

1. [1910s–40s] one’s criminal occupation.

2. [1910s+] (US Und.) any crime that depends not upon violence/coercion but on ‘lightness of touch and quickness of wit’ (Maurer, The Big Con 1940), e.g. professional confidence trickery, pickpocketing, professional gambling, circus/carnival work.

3. in attrib. use of sense 1.

4. [1910s+] as the grift, the world of crime; confidence trickery.

5. [1920s] in ext. use of sense 1, a non-criminal occupation.

6. [1920s–50s] the monetary proceeds of corruption, political bribery etc.

7. [1930s] (US Und.) the proceeds of a theft.

8. [1930s–40s] a plan, a scheme, an intention.

9. [1950s] an opinion.

10. see grifter n. (1)

In phrases

on the grift

[1990s+] working as a confidence trickster, gambler etc.