Lewis & Short

† synŏdĭcus, a, um, adj., = συνοδικός,

  1. I. going or coming together, synodical: luna, i. e. when in conjunction with the sun, Firm. Math. 3, 6; 4 praef. fin.
  2. II. According to the decrees of the synod, Cassiod. Hist. Eccl. 4, 21; 9, 13.
    Hence, adv.: synŏdĭcē, in accordance with the synod’s decrees, Cassiod. Hist. Eccl. 4, 25.