ὑπόβᾰσις · hypobasis — LSJ
going down, retiring, of the Nile floods, Str. 17.1.4; καθʼ ὑπόβασιν downwards, in bandaging, Sor. Fasc. 58; καθʼ ὑπόβασιν τῆς τῶν πρωτείων τάξεως downwards through the series, Ptol. Tetr. 46; οὕτω καθʼ ὑπόβασιν μέχρις ἀπείρου and so on ad infinitum, S.E. M. 9.306, cf. P. 3.87; successive diminution, of the terms in a series, opp. προκοπή, Iamb. in Nic. p.19P.
in Neoplatonism, declension, descent from eternity to the world, etc. (v. ὑποβαίνω IV), Procl. in Prm. p.492 S., Inst. 21,97, al., in Ti. 2.206 D., al., Aristid.Quint. 3.10; ὑ. ἑβδοματική Dam. Pr. 205; ἡ κατʼ οὐσίαν αὐτῶν ὑπεροχή τε καὶ ὑ. Hierocl. in CA 1p.419M., cf. Simp. in Ph. 774.21.
moral declension, Plot. 1.8.7; declension from perfect health, Aët. 4.1.
stooping or crouching down, esp. of a horse that lowers itself to take up the rider, X. Eq. 1.14; cf. ὑποβιβάζω II.
basement, pedestal, foot, Semus 15, Test.Epict. 8.23, IGRom. 4.685.16 (Sebaste), J. AJ 8.3.6.