a lemon lolli is when a guy gets his asshole sucked on while he takes a piss. lemon represents the act of urination and the 'lolli' is associated with the baloon knot being sucked on, hence the lemon lolli.
Due to the lack of genital stimulation from a lemon lolli, this act is most often enjoyed by looli loolies (urban dictionary term for homosexuals)
that girl gave me a lemon lolli last night , and im not talking about the hard candy. ohhhhh BOIIII!!