3.One of the light, flat growths forming the plumage of birds, consisting of numerous slender, closely arranged parallel barbs forming a vane on either side of a horny, tapering, partly hollowshaft.
5.A small opening or depression similar to a navel, as the hollow at the base of the shell of some gastropod mollusks, one of the openings in the shaft of a feather, or the hilum of a seed.