Green’s Dictionary of Slang

spliff v.

to smoke a marijuana or hashish cigarette.

2000		Indep. Rev. 19 Feb. 8: McLagan [...] drank and spliffed and tripped.
2016		Journal News (Hamilton, OH) 7 June 24/1: You don’t have to recite, ‘Forgive me, Willie Nelson, for I have spliffed’.

In derivatives

spliffed out (adj.) (also spliffed up)

intoxicated by cannabis;also fig.

1989		L.A. Times 5 Mar. 89/2: Metallic guitar whizzums gave the music more of an edge than the spliffed out riffs.
1991		De La Soul ‘Afro Connections 🎵 I get spliffed, get a stiff.
1994		Guardian 5 July 5/1: ‘We’re usually drunk anyway — or spliffed up’.
1996		Sydney Morn. Herald 2 Aug. 55/3: Dub has [...] enjoyed a renaissance among spliffed-out club heads.
2004		M.C. Strong Great Rock Discography 949: KAYA (1978) carried on in a similar vein with the spliffed-out ‘Easy Skanking’.
2005		N. Hasted Dark Story of Eminem 80: [...] extra-musical efforts were usually limited to lame spliffed-up ‘skits’ between tracks.
2007		Skins ser.1 ep.1 [TV script] We get a girl catastrophically spliffed up.
2014		Baltimore Sun (MD) 16 Apr. T26/2: It is finally and indisputably spring [...] There is nothing better than getting all spliffed out [...] and stepping out.