A.anything that comes off the surface:
I. of liquids, foam, froth, in Hom. of the sea, Od.12.238, al.; “ἁλὸς ἄ.” 5.403, cf. Tim.Pers.95, A.R.2.570; θοὴν ἀπερεύγεται ἄχνην, of a river, D.P.693: Medic., exudation, Hp.Int.1; οἰνωπὸς ἄ. froth of wine, E. Or.115; ἄχνα οὐρανία dew of heaven, S.OC681 (lyr.); δακρύων ἄχνα dewy tears, Id.Tr.848 (lyr.); also ἄχνη πυρός, i.e. smoke, A.Fr. 336.
II. of solids, chaff, in pl., “ὡς δ᾽ ἄνεμος ἄχνας φορέελ” Il.5.499; καρπόν τε καὶ ἄχνας ib.501; down on the quince, “μῆλον λεπτῇ πεποκωμένον ἄ.” AP6.102 (Phil.); ἄχνη ἡ ἀφ᾽ ἡμιτυβίου fluff, shreds, used for lint, Hp.Art.37; “ὀθονίου” Id.Mochl.2; ἄ. Λυδῆς κερκίδος, of finespun fabrics, S.Fr.45; ἄ. χαλκίτιδος metallic dust, Plu.2.659c, cf. Orph.L.455; ἄχναι wall-decorations, dub. in Aret.CA1.1 (stramina Cael. Aur.).