Source : Webster's Revised Unabridged Dictionary (1913)

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.

   {Under covert} (Zo["o]l.), one of the feathers situated
      beneath the bases of the quills in the wings and tail of a
      bird. See Illust. under {Bird}.