ἀχᾰνής · achanēs — LSJ
not opening the mouth, of one mute with astonishment, Hegesipp.Com. 1.25, Plb. 7.17.5, Luc. Icar. 23, Alciphr. 3.20; also διʼ ἀχανοῦς through a narrow opening, Thphr. Vent. 29.
yawning, κρημνός Timae. 28; χάσμα AP 9.423 (Bianor), J. AJ 7.10.2; without a lid, Hero Aut. 28.4; wide-mouthed, τεῦχος Diocl. ap. Orib. 5.4.2, cf. Antyll. ib. 44.8.12; open, ἀ. καὶ ἀνώροφος νεώς D.C. 37.17; open, unoccupied, of building land, POxy. 1702.3 (iii A. D.); χάσμα Parm. 1.18; σκότος LXX Wi. 19.17, cf. Lyr.Anon. in PFay. 2ii20; τὸ ἀχανές the yawning gulf, Arist. Mete. 367a19; ἡ ἀ. χώρα Ph. 1.7; ἀχανές· τὸ μὴ ἔχον στέγην . . ἐπὶ τοῦ λαβυρίνθου, S. Fr. 1030; ὄψει πάντα ἀχανῆ PMag.Par. 1.1
generally, vast, immense, στράτευμα Plu. Herod. 2.866b; πέλαγος Id. Cic. 6, Jul. Or. 4.142c.