Can I Move An iTunes Movie Rental To Another Device?
If you first download the rented movie to your Mac, then you can transfer it to another Mac, iPhone, iPad, Apple TV, etc. If it's a high definition (HD) movie rental, you can only move it to other devices that support HD playback. Once transfer, the rental will remove itself from the original device as iTunes movie rentals are only able to be stored in one place at a time.
If you first download the rented movie to a non-Mac device like an iPad, iPhone, or Apple TV, you will not be able to tranfer it to another device or Mac.