a painful, tender focal mass lesion on one of the plantar interdigital nerves of the foot, most often that which is situated between the third and fourth metatarsal bones; attributed to either compression of the nerve between the heads of the adjacent metacarpal bones, or traction being placed on the nerve as it crosses the anterior edge of the deep transverse metatarsal ligament. SYN: Morton metatarsalgia, Morton neuralgia.