The term defined as the remnants of dead, massive stars is "black holes."
1. Black holes are formed when massive stars run out of fuel and collapse under their own gravity.
2. They are incredibly dense regions in space where gravity is so strong that nothing, not even light, can escape from them.
3. Black holes can vary in size, from stellar-mass black holes (formed from the remnants of massive stars) to supermassive black holes found at the centers of galaxies.
Therefore, among the options provided, black holes are the entities that are defined as the remnants of dead, massive stars.
