Lewis & Short

Ăchĕlōĭus, a, um, adj. [Achaemenes q. v.].

  1. I. Pertaining to the river Achelous, Verg. G. 1, 9; Ov. H. 16, 265: Callirrhoë, daughter of Achelous, id. M. 9, 413.
  2. II. Aetolian: heros, i. e. Tydeus, the son of Oeneus, king of Aetolia, Stat. Th. 2, 142.