transverse plane anteroposterior axis base of support frontal plane circumduction sagittal plane longitudinal axis average angular velocity centripetal force transverse axis cardinal plane angular displacement 1. A plane that passes through the midpoint or center of gravity of the body. 2. An external force directed toward the axis of rotation of an object moving in a circular path. 3. An imaginary plane running anterior to posterior and superior to inferior that divides the body into right and left parts; anteroposterior plane. 4. An imaginary plane running from side to side and anterior to posterior that divides the body into superior and inferior parts; horizontal plane. 5. An imaginary plane running side to side and superior to inferior that divides the body into anterior and posterior parts; coronal plane; lateral plane. 6. Angular displacement divided by the time it took for that angular displacement to occur with direction of rotation indicated; measured in units of angular displacement divided by units of time or expressed as radians per second, degrees per second, or revolutions per second; a vector quantity. 7. Any of the imaginary lines running from left to right and perpendicular to the sagittal planes; horizontal axis; frontal axis; mediolateral