Though unambiguous, the gloss -- paralleled, according to Adler, in the Ambrosian Lexicon -- is at odds with classical usage. The neuter noun ἀγκυρηβόλιον occurs in a fragment of Democritus quoted twice by Plutarch (Moralia 317A, 495E), and, as LSJ s.v. note, is the equivalent there of ἀγκυροβόλιον , "place of anchorage".
On ancient anchors see generally Lionel Casson, Ships and Seamanship in the Ancient World (Baltimore & London 1995) 252-7.