Q: I have this plant growing in my compost pile. It has large leaves and a very prickly stem. It is growing very rapidly.
A: It’s a squash of some sort. It resulted from seeds that you threw out from a squash you ate recently. The squash you have may not completely resemble the one you discarded, since your seeds might have come from a cross-pollinated plant.
You can wait a few weeks to see what happens. The fruit is completely edible if harvested when tender.