(adjective) : sībĭlus, a, um, 1. sibilus
* Hissing, whistling (poet.; occurring, on account of the metre, only in the form sibila; cf. 1. sibilus init.): colla (colubrae),Verg. G. 3, 421; id. A. 5, 277; cf. ora (anguium),id. ib. 2, 211: coma torvae frontis (Panis),Val. Fl. 3, 50.

sībĭlus | sībĭla (noun M) : (collat. form, abl., sibilu, Sisenn. ap. Prisc. p. 715 P.—In plur. in the poets, prob. merely for the sake of the metre: , ōrum; cf. 2. sibilus
* Init.; but in Cic. sibili), m.cf. σιφνός, σιβλός, hollow; Angl. S. and Engl. sipan, sip; O. H. Germ. sip, Germ. Sieb, a sieve; regarded by the ancients as imitation of a natural sound; cf. Quint. 8, 6, 31; Auct. Her. 4, 31, 42, a hissing, a whistling (class.)
* In gen.
* Sing., of men: sibilo dare signum,Liv. 25, 8 fin.—Of cattle: (boves) sibilo allectari,Col. 2, 3, 2.—Of things: clamor tonitruum et rudentum sibilus, Poët. ap. Cic. Fam. 8, 2, 1: (arbor) Loquente saepe sibilum edidit coma,Cat. 4, 12: venientis sibilus austri,Verg. E. 5, 82: sibilu significare alicui, Sisenn. ap. Prisc. p. 715 P.
* In partic., a contemptuous hissing, a hissing at or off (usually in plur.).
* Sing.: sibilum metuis?Cic. Pis. 27, 65.
* Plur.: e scaenā sibilis explodi,Cic. Rosc. Com. 11, 30: aliquem sibilis consectari,id. Att. 2, 18, 1: crebris totius contionis sibilis vexatus,Val. Max. 7, 3, 6ext.;Cic. Sest. 59, 126; cf.: gladiatorii sibili, id. Fragm. ap. Charis. p. 61 P.: quā dominus, quā advocati sibilis conscissi,id. Att. 2, 19, 3.