A.extending inwards, under the surface of the flesh, enclosed, “τὰ συριγγώδη καὶ ὅσα ὕ. ἐστι καὶ ἔντοσθε κεκοιλασμένα” Hp.Medic.11; ὅσα μὲν ἔχει στόμα μέγα καὶ οὐ ταχὺ συμφύεται, ταῦτα καίειν δεῖ, ὅπως ἡ ἐσχάρα ἐκεῖ πέσῃ: οὕτως γὰρ οὐκ ἔσται ὕπουλα, i.e. there will be no internal accumulation of pus, Arist.Pr.863a12; also of the part affected, festering, purulent, “σῶμα” Cratin.351, cf. Plu.Lyc.4; “ἐπιληψίαι” Gal.Vict.Att. 1; “σπλήν” Pl.Ti.72d.
2. metaph., with festering sores underneath, unsound, hollow, οἰδεῖ καὶ ὕ. ἐστιν [ἡ πόλις] Id.Grg.518e; ὕ. τὴν ψυχὴν ποιήσει ib.480b; “ὕ. τέλμα” treacherous, Plu. Rom.18; ὕ. εὐνομία (v.l. αὐτονομία) hollow, unreal, Th.8.64; “ὕ. ἡσυχία” D.18.307; applied to the Trojan horse, S.Fr.1105; κάλλος κακῶν ὕπουλον a fair outside, but fraught with ills below, Id.OT 1396; “ὕ. μάντευμα” false, fallacious, Paus.3.7.3; “φαντασίαι” Gal.7.203; “λόγοι” Babr.44.4; of persons, false, deceitful, “ἀνὴρ ὕ. δίκτυον κεκρυμμένον” Men.Mon.587; “δόλιοι καὶ ὕ.” Phld.Ir.p.60 W., cf. Plu. Caes.60, etc.; “ὕ. οἱ Ἀττικοί” Dicaearch.1.4; concealed, [δόξαι], ἔχθρα, Phld.D.1.24, D.H.3.28; of evils, festering within, “οἴημα” Plu.2.44a; στάσεις ib.329b. Adv., -ως διακεῖσθαί τινι to be secretly hostile to one, Plb.10.35.6; ὑ. ἀκροᾶσθαι render a hollow obedience, Plu.Luc.21; joined with δολίως, Epigr.Gr.387 (Apamea Cibotus). (Perh. from ὑπείλλω, lit. shut up, suppressed; ὕπουλον = a 'gathering'.)
