Bunny noun – (usually informal) especially a young rabbit. Pin-up and bunny are semantically related in attractive woman topic. In some cases you can use "Pin-up" instead a noun "Bunny".
Pin-up noun – A very pretty girl who works as a photographer's model. Bunny and pin-up are semantically related in attractive woman topic. You can use "Bunny" instead a noun phrase "Pin-up".