Definition.com
Free play (n.) of the faculties, their harmony, cannot be thought, only felt: it makes itself known as the lightened play of imagination and understanding enlivening each other.
3 definitions
Definition.com
Free play (n.) of imagination and understanding is the state of mind when no determinate concept ties the cognitive powers to a rule — and it is this state, not the object, that we feel as beauty.
Definition.com
Free play (n.) of the imagination, Kant's phrase, names the free transformations an image undergoes by spontaneity — until the will reclaims its rights, wants to develop the image, and everything breaks.