Green’s Dictionary of Slang

(UK drugs) a form of synthetic cannabis, a more potent form of THC.

2016		Guardian 2 May 1/1: Synthetic cannabis is having a ‘devastating impact’ in British prisons [...] Sold as ‘spice’ and ‘black mamba’.
2019		Headie One ‘Ball in Peace 🎵 Can't tell me 'bout hustle, jailhouse, I done it with spice and hash.
2023		Rayman & Blau Riker’s 170: K2 is fucking crazy in there. They call it ‘plain’ or “deuce.” A lot of the guys who were smoking were guys who were addicted to heroin and crack on the outside, and they just want some escapism.
2023		N. Gerrard in Guardian 9 Dec. 🌐 [Homeless women] often use drugs to dull their pain: spice, which is cheap; opiates or synthetic opiates.