Lewis & Short

sēcessĭo, ōnis, f. [secedo, I. B.].

  1. I. (Acc. to secedo, I. B. 1.) A going aside to consult, etc., a withdrawal: seductiones testium, secessio subscriptorum, Cic. Mur. 24, 49: milites vesperi secessionem faciunt, Caes. B. C. 1, 20, 1: primores, secessione factā, etc., having withdrawn, Liv. 21, 14, 1.
  2. II. (Acc. to secedo, I. B. 2.) A political insurrectionary withdrawal or separation; a schism, secession (the prevailing signif. of the word; syn.: defectio, seditio): ultima rabies secessio ab suis habebatur, Liv. 7, 40, 2: secessionem tu illam existimasti, Caesar, initio, non bellum, Cic. Lig. 6, 19: tum demissi populo fasces, tum provocationes omnium rerum, tum secessio (pern. secessiones) plebis, etc., Cic. Rep. 1, 40, 62 Mos. N. cr.; cf. Liv. 2, 32 sq.; 3, 39; Caes. B. C. 1, 7: per secessionem armati Aventinum occupavere, Sall. J. 31, 17: in secessione Crustumerinā, Varr. L. L. 5, § 81 Müll.; cf.: secessio ab decemviris facta est, Liv. 3, 51: in Aventinum montem secessionem factam esse, id. 2, 32.