means abnormally flexible.

abnormal laxity of the joint in one or more directions

(also called: double-jointed; loose-jointed) -- 1. Having unusually lax muscles and connective tissue, and joint sockets that allow an extreme range of motion. 2. [Hypermobility test designed by Peter Beighton] One who can perform at least three of the following nine skills: place both palms on the floor with the legs straight, hyperextend the right or left elbow 15 degrees, hyperextend the right or left knee 15 degrees, passively place either thumb against the same forearm, passively bend the fingers of either hand backward 90 degrees with respect to the back of the hand.