2) Oral sex performed on someone in a park/carpark/shop doorway. A person does not necessarily have to be a tramp to perform or receive Tramp Nosh but it is reasonable to assume that at least one participant may be, due to the scabby choice of location.
"Nah, throw it down, man. Let it become tramp nosh."
2) Claire regretted her choice to remain sober and be the designated driver as soon as she approached her car and noticed, all too clearly, the gentleman reclining against it, recieving an enthusiastic tramp nosh from a woman in pink pvc and hair glitter.