What is a baby rabbit called?

Let's call the baby rabbit "Pip".

Pip is a tiny bundle of fluff, barely bigger than a human hand. His fur is a soft, downy grey, though it might change color as he grows older. His eyes are still closed, or perhaps just barely opening, revealing a pinkish hue. His ears are small and folded, like velvet petals. He spends most of his time nestled amongst his siblings in a snug burrow, occasionally twitching his nose as he takes tiny breaths. He's completely dependent on his mother for warmth, nourishment (mother's milk), and protection from predators. He's learning to navigate his world using his incredible sense of smell and hearing. While he can't yet hop very well, he attempts clumsy little movements, his tiny legs kicking out in a flurry of activity. Pip, and his siblings, are a vulnerable part of their ecosystem, facing numerous threats including foxes, hawks, and even other animals. His future depends on the health of his mother, his siblings' survival, and the safety of their habitat.