Entry 2 senses Webster, 1913 Ethereous · E·the·re·ous · IPA 01 a. Formed of ether; ethereal. 1. Formed of ether; ethereal.[Obs.] “This ethereous mold whereon we stand.” — Milton. 2. Pertaining to, or resembling, ether.(Chem.) Phrases & compounds Ethereous oil — See Ethereal oil, under Ethereal.