A.fold, doubling, Gal.2.710: but usu.,
II. porous substance between the double plates in the bones in the skull, Hp.VC1, 17, Heliod. ap. Orib.46.9.4, Ruf.Onom.135: generally, spongy core of bone, Paul.Aeg.6.77; also, tissue between layers of intestine, Aret. SD2.9: hence,
2. weak spot, flaw in metal, Pl.Sph.267e, Ph. Bel.71.28, Plu.2.802b: metaph., αἱ δ. τῆς ψυχῆς ib. 715f, cf. 441d; 'patchiness', Plot.5.2.1; also, concealed sense, in oracles, Plu.2.407c.
III. hollow sting of the scorpion, Ael.NA9.4.