n. (pl.-ia) mass of nerve cells; nerve centre; small cyst in tendon sheath, especially at wrist or ankle. ganglionectomy, n. removal of ganglion. ganglionitis, n. inflammation of ganglion. ganglial, gangliar, ganglionic, a.gangliate(d), ganglionated, a. having ganglia. gangliform, ganglioform, ganglioid, a. like ganglion.