Lewis & Short

conclūsĭo, ōnis, f. [concludo].

  1. I. A shutting up, closing (rare, not in Cic.).
    1. A. Abstr.: palpebrarum, Cael. Aur. Acut. 2, 3 and 10.
      1. 2. In milit. lang., a hostile shutting in, a siege, blockade: diutina, Caes. B. C. 2, 22; so Nep. Eum. 5, 7.
        In plur., Vitr. 5, 9 fin.
    2. * B. Concr.: portuum, an enclosure, Vitr. 5, 12.
  2. II. (Acc. to concludo, II. B. and D.; freq. in Cic. and Quint.) A conclusion, end: in extremā parte et conclusione muneris ac negotii, Cic. Q. Fr. 1, 1, 16, § 46.
    1. B. The conclusion of a discourse, peroration: conclusio est exitus et determinatio totius orationis, Cic. Inv. 1, 52, 98: tum autem alii conclusionem orationis et quasi perorationem collocant, id. de Or. 2, 19, 80; Auct. Her. 2, 30, 47; cf.: perorationem conclusionem alii vocant, Quint. 6, 1, 1; cf. also id. 8, 5, 13.
    2. C. In rhet. lang., a period, Cic. de Or. 2, 8, 34; 3, 44, 174; id. Brut. 8, 33; id. Or. 50, 169; 51 init.; Quint. 9, 4, 22; 9, 4, 57; 9, 4, 123 et saep.
    3. D. In philos., the conclusion in a syllogism, the consequence: conclusio est, quae brevi argumentatione ex eis, quae ante dicta sunt aut facta, conficit, quid necessario consequatur, Auct. Her. 4, 30, 41; Cic. Inv. 1, 29, 44 and 45; id. Div. 2, 49, 103; Quint. 5, 14, 1; 5, 14, 20; 7, 3, 14; 5, 10, 2; 5, 10, 7; 9, 3, 98 Cornif.; Gell. 2, 8, 8.