Lewis & Short

păcisco, ĕre, 3, v. n. and a. [collat. form of dep. paciscor, q. v.], to agree, contract, bargain, covenant (class. only in perf. part. pass.): id quoque paciscunt, Naev. ap. Non. 474, 17: paciscit, obsides ut reddant, id. ib. 18.
Hence, pactus, a, um, in pass. signif., agreed upon, settled, determined, covenanted, stipulated (class.).

  1. A. In gen.: pactum pretium, Cic. Off. 3, 29, 107: pacta praemia, id. Q. Fr. 3, 3, 2: dies, id. Cat. 1, 9, 24: merces, Hor. C. 3, 3, 22: foedus, Cic. Sest. 14, 33: cum hoste pactae induciae, id. Off. 1, 10, 33.
    In the abl. absol.: quidam pacto inter se ut victorem res sequeretur, ferro decreverunt, by agreement, Liv. 28, 21, 5; Sil. 14, 97.
  2. B. In partic., betrothed: haec tibi pacta’st Callicli filia, Plaut. Trin. 5, 2, 59: cujus filio pacta est Artavasdis filia, Cic. Att. 5, 21, 2: alii pacta puella, Tac. A. 1, 55: Turnus, cui pacta Lavinia fuerat, Liv. 1, 2: conjux, Verg. A. 10, 722.
    Hence, as subst.
    1. 1. pacta, ae, f., a betrothed woman: gremiis abducere pactas, Verg. A. 10, 79: pacta ejus, Menelai filia, Vell. 1, 1, 3; Juv. 6, 200.
    2. 2. pactus, i, m., a betrothed husband, a man engaged or promised in marriage: proles Amissum didicere patrem, Marpissaque pactum, Stat. Th. 3, 172.
    3. 3. pactum, i, n., an agreement, covenant, contract, stipulation, compact, pact (cf.: conventio, pactio, obligatio): pactum est, quod inter aliquos convenit, Cic. Inv. 2, 22, 68; cf. Auct. Her. 2, 13, 20: pacta et promissa semperne servanda sint, Cic. Off. 3, 24, 92: mansit in condicione atque pacto, id. Verr. 1, 6, 16: pacti et conventi formula, id. Caecin. 18, 51; cf.: ex pacto et convento, id. Att. 6, 3, 1: pacta conventaque, Sen. Ben. 3, 15, 1: stare pacto, Liv. 9, 11: pactum violans, Vulg. Mal. 2, 10 et saep.
      Hence (eccl. Lat.), the covenant of God: dereliquerunt pactum Domini, Vulg. Deut. 29, 25; id. 3 Reg. 11, 11; id. 2 Par. 6, 14.
      Poet.: sacrum, i. e. a marriagecontract, Val. Fl. 8, 401; cf. Juv. 6, 25.
        1. (β) Transf., in gen., abl. pacto (like ratione and modo), manner, way, means (class.): percontat Aeneas, quo pacto Troiam urbem liquerit, Naev. Bell. Pun. 2, 1: si non fecero ei male aliquo pacto, Plaut. Bacch. 3, 6, 27; id. Am. prol. 137: nescio quo pacto semper hoc fit, how, Cic. Mur. 21, 43; id. Quint. 17: non tacebo umquam alio pacto, nisi, etc., Plaut. Rud. 5, 3, 46: aliquo pacto verba his dabo, Ter. Heaut. 4, 4, 13: quoquo pacto tacito est opus, id. Ad. 3, 2, 44: si nullo alio pacto, id. Phorm. 2, 1, 71: alio pacto docere, Cic. Inv. 1, 21, 30: fieri nullo pacto potest, ut, etc., id. Fin. 1, 8, 27; Ter. And. 1, 5, 12: servi mei si me isto pacto metuerent, Cic. Cat. 1, 7, 17; Hor. Ep. 1, 6, 10; 1, 8, 13: hoc pacto, Verg. G. 2, 248.

pactum, i, n., v. pacisco fin.