inverted pleat: a box pleat reversed so that the fullness is turned inward
pleat: any of various types of fold formed by doubling fabric back upon itself and then pressing or stitching into shape
parasympathetic nervous system: originates in the brain stem and lower part of the spinal cord; opposes physiological effects of the sympathetic nervous system: stimulates digestive secretions; slows the heart; constricts the pupils; dilates blood vessels