Charlton T. Lewis, Charles Short, A Latin Dictionary

I.a public prayer or supplication, a religious solemnity in consequence of certain (fortunate or unfortunate) public events; a day set apart for prayer, either by way of thanksgiving or of religious humiliation, genuflection (cf. obsecratio): “atque etiam supplicatio diis immortalibus pro singulari eorum merito meo nomine decreta est, etc.,” Cic. Cat. 3, 6, 15: “praetor urbanus supplicationes per dies quinquaginta ad omnia pulvinaria constituat,” id. Phil. 14, 14, 37; so, “decreta ad omnia pulvinaria,” id. Cat. 3, 10, 23: “quorum (prodigiorum) averruncandorum causā supplicationes in biduum senatus decrevit,” Liv. 10, 23, 1; 5, 23, 4: “supplicationem habere,” id. 10, 47, 7; 31, 9, 6: “fuit,” id. 37, 3, 5.—Sometimes such a supplicatio was decreed in honor of a victorious general to precede his triumph: “cui uni togato supplicationem senatus decreverit,” Cic. Sull. 30, 85: “ex litteris Caesaris dierum viginti supplicatio a senatu decreta est,” Caes. B. G. 4, 38 fin.; 7, 90 fin.; Cic. Prov. Cons. 11, 27; id. Pis. 3, 6; Cato ap. Cic. Fam. 15, 5, 2: “dies quindecim supplicatio decreta est,” Caes. B. G. 2, 35: “supplicatio diem unum Romae, alterum in Capenati agro indicta est,” Liv. 27, 4, 15: “diem unum supplicatio fuit ob, etc.,” id. 41, 28, 1: “in quatriduum supplicationes decernere,” id. 5, 23, 3; 37, 47, 4; Suet. Caes. 24 fin. al.