Green’s Dictionary of Slang

gunston n.

[var. on gungeon n.]

(S.Afr. drugs) marijuana.

[SA]J. Matthews The Park and Other Stories (1983) 42: ‘Dey catch me wit’ a parcel gunston.’ ‘What’s gunston?’ Bruce asked innocently. [...] ‘Dagga, yer kroets!’ the youth said disgustedly.