† ˈætiologueObs.rare—1. [f.Gr. αἰτία cause, ground + λόγος speech. Cf. ætiology 1.] The cause assigned, or reason annexed to a statement. 1632Bp. Smyth Serm. 43 In the aetiologue following, namely, in these words: Thou hast the words of euerlasting life.