Lewis & Short

Symplēgădes, um, f., = Συμπληγάδες (that strike together).

  1. I. Two rocky islands in the Euxine that, according to the fable, floated about dashing against and rebounding from each other, until at length they became fixed on the passage of the Argo between them, Mel. 2, 7, 11; Plin. 4, 13, 27, § 92; 6, 12, 13, § 32; Ov. M. 15, 338; Hyg. Fab. 19.
    In sing. Symplegas, Val. Fl. 4, 221; Luc. 2, 718; gen. Symplegados, Val. Fl. 5, 300; acc. Symplegada, Claud. in Eutr. 2, 30.
  2. II. Transf.: symplēgas, ădis, f.; as an appellative, a joining together, cohesion: praebente algam densi symplegade limi, Rutil. Itin. 1, 461.
    Of the buttocks, Mart. 11, 99, 5; Aus. Epigr. 108, 8.