to turn into a prone position; to rotate (the hand or forearm) so that the surface of the palm is downward or toward the back; to turn (the sole of the foot) outward so that the inner edge of the foot bears the weight when standing.
(in vertebrates) to rotate (any limb or joint) in a similar manner.
?v.i.
to become pronated.
Random House Unabridged Dictionary, Copyright 1997, by Random House, Inc., on Infoplease.