Lewis & Short

ac-cumbo (adc.), cŭbui, cŭbĭtum, 3, v. n., to lay one’s self down at a place; and hence, to lie somewhere.

  1. I. In gen. (so very rare): in via, Plaut. Most. 1, 4, 13; of one swimming: summis in undis, Manil. 5, 429.
  2. II. In part.
    1. A. To recline at table, in the manner in which the Romans (and finally even the Roman women, Val. Max. 2, 1, 2) reclined, after luxury and effeminacy had become prevalent. While they extended the lower part of the body upon the couch (triclinium, lectus triclinaris), they supported the upper part by the left arm upon a cushion (or upon the bosom of the one nearest; hence, in sinu accumbere, Liv. 39, 43; cf. ἀνακεῖσθαι = εἶναι ἐν τῷ κόλπῳ τινός, Ev. Ioh. 13, 23), the right hand only being used in taking food: hoc age, adcumbe, Plaut. Pers. 5, 1, 15; so id. Most. 1, 3, 150, etc.; Cic. Verr. 2, 5, 31; id. Mur. 35; Liv. 28, 18; c. acc.: mensam, Att. ap. Non. 415, 26; Lucil. Sat. 13; ib. 511, 16: cotidianis epulis in robore, Cic. Mur. 74: in convivio, id. Verr. 1, 66: in epulo, Cic. Vatin. 12: epulis, Verg. A. 1, 79; tecum, Plaut. Bacch. 5, 2, 75; absol., Cic. Deiot. 17.
      Since three persons usually reclined upon such a couch (cf. Cic. Pis. 27), these expressions arose: in summo (or superiorem, also supra), medium and imum (or infra) adcumbere; and the series began on the left side, since they lay supported by the left arm. The whole arrangement is explained by the following figure: [??] Among the three lecti, the lectus medius was the most honorable; and on each lectus, the locus medius was more honorable than the summus; and this had the preference to the imus or ultimus. The consul or other magistrate usually sat as imus of the lectus medius (fig. no. 6), in order that, by his position at the corner, he might be able, without trouble, to attend to any official business that might occur. The place no. 7 seems, for a similar reason, to have been taken by the host. See on this subject Salmas. Sol. p. 886; Smith’s Antiq.; Becker’s Gall. 3, p. 206 sq. (2d ed.); and Orell. excurs. ad Hor. S. 2, 8, 20. This statement explains the passages in Plaut. Pers. 5, 1, 14; id. Most. 1, 1, 42; id. Stich. 3, 2, 37, etc.; Cic. Att. 1, 9; id. Fam. 9, 26; Sall. Fragm. ap. Serv. ad Verg. A. 1, 702; Hor. S. 2, 8, 20.
    2. B. In mal. part. (rarely), Plaut. Bacch. 5, 2, 73; Men. 3, 2, 11; 5, 9, 82.