Green’s Dictionary of Slang

an act of urination, also as v.

1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 5: Gipsy’s kiss: Make water.
1972		Galton & Simpson ‘The Desperate Hours’ Steptoe and Son [TV script] I went outside for a gipsy’s.
1977		D. Powis Signs of Crime 187: Gypsy’s (kiss) Urination (piss): ‘Watch my drink, I’m going for a gypsy’s.’.
1981		P. Wright Cockney Dialect and Sl. 107: An informant tells me that gipsy’s for a gipsy’s kiss ‘piss’ was used innocently by two of his clergymen friends.
2003		B. Dark Dirty Cockney Rhy. Sl. 62: I’m off for a gypsy’s kiss.
2011		J.J. Connolly Viva La Madness 170: In some bushes, having a gypsy’s kiss. Reckons he’s got a weak bladder.