Lewis & Short

dēfectĭo, ōnis, f. [deficio].

  1. I. Defection, desertion, rebellion, revolt.
    1. A. Lit.: rebellio facta post deditionem, defectio datis obsidibus, Caes. B. G. 3, 10; 5, 26; 6, 3, 4; Liv. 7, 42; 23, 12: Ampsivariorum a tergo, in the rear (of Caesar), Tac. A. 2, 8; 4, 24 et saep.: subita defectio Pompeii, Cic. Q. Fr. 1, 4, 4 al.: imperii, from the empire, Just. 41, 2, 1.
    2. * B. Trop.: intemperantia, quae est a tota mente et a recta ratione defectio, Cic. Tusc. 4, 9, 22.
  2. II. (Acc. to deficio, no. III.) A failing, failure, deficiency, want, disappearance.
        1. a. Lit. (so most freq.): ista ipsa defectio virium adolescentiae vitiis efficitur saepius quam senectutis, Cic. de Sen. 9, 29: aquarum, Frontin. Aquaed. 91: pecuniae, Macr. Sat. 2, 5: rerum, Sen. Q. N. 4, 2.
        2. b. Esp. of the obscuration of the heavenly bodies, an eclipse: solis defectiones itemque lunae praedicuntur in multos annos, Cic. Div. 2, 6, 17; 1, 49 fin.; id. N. D. 2, 61; id. Rep. 1, 14 fin.; Sen. Q. N. 1, 12; Quint. 1, 10, 47; Tac. A. 1, 28 et saep.
        3. c. Also (sc. virium), exhaustion, faintness, swooning, fainting (post-Aug. prose), Plin. 23, praef. § 4: animae, a swoon, Cels. 7, 33; Suet. Cal. 50: alvo usque ad defectionem soluta, id. Vesp. 24; cf. id. Tib. 73: recreandae defectioni cibum adferre, Tac. A. 6, 56 (50); cf.: defectione perire, by exhaustion, i. e. by disease, Sen. N. Q. 2, 59, 11: in cunctis renibus, Vulg. Nahum 2, 10.
        4. d. In the later grammarians, an ellipsis: dicere aliquid per defectionem, by ellipsis, elliptically, Gell. 5, 8, 3; 12, 14, 3; Macr. Sat. 6, 8 al.
    1. * B. Trop.: Quintus frater omnia mittit spei plena, metuens credo defectionem animi mei, my want of courage, despondency, Cic. Att. 3, 18.