Lewis & Short

concessĭo, ōnis, f. [concedo, I. B. 3.], an allowing, granting, conceding, permission, leave (rare, but in good prose).

  1. I. In gen.: agrorum, Cic. Agr. 3, 3, 11; Tac. A. 3, 73: praemiorum, Planc. ap. Cic. Fam. 10, 8, 3: concessio, ut peculiare aliquid in fundo pascere liceat, Varr. R. R. 1, 17, 7: vestra, Cic. Att. 3, 24, 1: competitorum, id. Tog. Cand. Fragm. 5 (8, 5, p. 21 B. and K.).
    1. B. A yielding, retiring: legis, Tert. adv. Marc. 5, 13.
  2. II. Esp., in rhet., a figure of speech, concession: cum aliquid etiam iniquum videmur causae fiduciā pati, * Quint. 9, 2, 51.
      1. 2. Jurid. t. t., a plea of confession and excuse or mitigation: concessio est, per quam non factum ipsum probatur ab reo, sed ut ignoscatur, id petitur, Cic. Inv. 2, 31, 94; 1, 11, 15; Auct. Her. 1, 14, 24.