Lewis & Short

ob-signo, āvi, ātum, 1, v. a., to seal, seal up a will, a letter, etc. (class.).

  1. I. Lit.
    1. A. In gen.: cedo tu ceram ac linum actutum: age obliga, obsigna cito, Plaut. Bacch. 4, 4, 96: cellas, id. Cas. 2, 1, 1: lagenas, Q. Cic. Fam. 16, 26: epistulam, Cic. Att. 8, 6, 1; id. Pis. 28, 71.
      Esp.: tabulas, testamenta, to sign and seal, as a witness: istam ipsam quaestionem, dicite, quis obsignavit? Cic. Clu. 66, 185: tabellas ejus rei condicionisque, id. Quint. 21, 67: testamentum signis adulterinis, id. Clu. 14, 41: obsignavit anulo, Vulg. Dan. 6, 17.
      Prov.: agere cum aliquo tabellis obsignatis, to deal with one with sealed writings, i. e. in the strictest form, Cic. Tusc. 5, 11, 33 (cf.: tamquam ex syngraphā agere cum populo, id. Mur. 17, 35): tabulas obsignare velle, would seal up the documents, i. e. would have no discussion, id. Pis. 28, 69.
    2. B. In partic.
      1. 1. To seal up the papers and effects of an accused person, Cic. Verr. 1, 19, 50.
        Hence,
      2. 2. To seal an accusation against one: qui contra Scaurum patrem suum obsignaverat, Cic. Scaur. Fragm. ap. Ascon.
      3. 3. To pledge or mortgage under one’s hand and seal: tria agri jugera ad aerarium obsignaverat, Val. Max. 4, 4, 7.
      4. 4. To close under seal, make fast: inane obsignari nihil solere, Cic. Div. 2, 70, 145; cf. the context.
  2. II. Trop., to stamp, impress: formam verbi, Lucr. 4, 567: aliquid obsignatum habere, to impress on the mind, id. 2, 581.