The Collaborative International Dictionary of English v.0.48:

Under \Un"der\, a.
   Lower in position, intensity, rank, or degree; subject;
   subordinate; -- generally in composition with a noun, and
   written with or without the hyphen; as, an undercurrent;
   undertone; underdose; under-garment; underofficer;
   undersheriff.
   [1913 Webster]

   Under covert (Zool.), one of the feathers situated beneath
      the bases of the quills in the wings and tail of a bird.
      See Illust. under Bird.
      [1913 Webster]