Green’s Dictionary of Slang

1. (US Und.) to trick a person for a second time.

1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 176/2: Reload. To sell a second lot of worthless stock to a previously victimized person, especially by accepting the first lot as part payment for the second at a ‘liberal’ exchange value.

2. (UK Und.) to ensnare a victim in a confidence game, e.g. three-card monte, by allowing them small victories, thus increasing their confidence (and bets) prior to taking their money.

1977

D. Powis Signs of Crime 199: Reload To ensnare a ‘mug’ by letting him think he is winning (at the three-card trick, for example) or has gained a smallish profit or advantage (in a confidence trick, for example), and then, while he is in the mood of false confidence and with his appetite whetted, to cheat him of all he possesses, or as the term has it ‘to send him to the cleaners’.

3. (UK drugs) to renew one’s supply of narcotics.

2011		J.J. Connolly Viva La Madness 280: A skaghead whose only exercise is building pipes and running to reload.
2020		G. Krauze What They Was 215: We give him the nine zeds [...] He says ah safe [...] I was looking to reload.