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supplĭcātĭo (subpl-), ōnis, f. [supplico]; in relig. lang., 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.