Mishnayos Oholos Perek 18 Mishnah 6

המהלך בבית הפרס – in a field where a grave was ploughed up in it.

על אבנים שיכול להסיטן – as for example on top of stones that are not lodged/placed and affixed in the ground and they can be moved on account of passing over them, and a human bone the size of a barleycorn is shaken from its position of strength, or rides upon a person or an animal [which cannot endure pressure and walks/treads upon them, the rider is impure, for since the strength at the bottom is bad/poor, on account of the load above, it was moved and it is as if he shakes the bone. But if if the strength of the one being driven has a strong legal right, the rider is not considered as if he shaking the bone. But how is that to be understood – that a person has a weak legal right? All that ride it and his knees and the surrounding parts knock against each other. But an animal whose strength is weak, all that ride it cause it to empty its bowels.

בהרים ובסלעים – even though they don’t bury a corpse there.

טמא – because of the dust of the Lands of the Nations that is rolled there.

בים ובשונית טהור (on the sea and on the beach/rocky cliffs – from the defilement of the soil/ground. That they (i.e., the Rabbis) decreed on the soil of the Land of the Nations to burn the heave-offering and Holy Things that touched its dust, for we don’t burn heave-offering or Holy Things that came to the sea or to the beach/rocky cliffs, for we don’t bury a corpse there, but they have the defilement of the Land of the Nations, for they (i.e., the Rabbis) decreed upon its airspace to suspend, that heave-offering and Holy Things that entered into the airspace of the Land of the Nations and didn’t touch its soil, we don’t eat it nor do we burn it.

בזעפו – where the sea rages.