Trunk of lymphatic tree organ part, each instance of which is either of the two lymphatic trunks (right and left) that drain some pulmonary, bronchopulmonary, tracheobronchial, tracheal, and parasternal lymphatic chains (lymph nodes and lymphatic vessels): that on the right side drains into some right lymphatic duct or subclavian vein, and that on the left into some thoracic duct or some subclavian vein.