sinus

sinus
    n 1: an abnormal passage leading from a suppurating cavity to
         the body surface [syn: {fistula}, {sinus}]
    2: any of various air-filled cavities especially in the bones of
       the skull
    3: a wide channel containing blood; does not have the coating of
       an ordinary blood vessel [syn: {venous sinus}, {sinus}]
    

Sinus \Si"nus\, n.; pl. L. {Sinus}, E. {Sinuses}. [L., a bent
   surface, a curve, the folds or bosom of a garment, etc., a
   bay. Cf. {Sine}, n.]
   1. An opening; a hollow; a bending.
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   2. A bay of the sea; a recess in the shore.
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   3. (Anat. & Zool.) A cavity; a depression. Specifically:
      (a) A cavity in a bone or other part, either closed or
          with a narrow opening.
      (b) A dilated vessel or canal.
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   4. (Med.) A narrow, elongated cavity, in which pus is
      collected; an elongated abscess with only a small orifice.
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   5. (Bot.) A depression between adjoining lobes.
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   Note: A sinus may be rounded, as in the leaf of the white
         oak, or acute, as in that of the red maple.
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   {Pallial sinus}. (Zool.) See under {Pallial}.

   {Sinus venosus}. [L., venous dilatation.] (Anat.)
      (a) The main part of the cavity of the right auricle of
          the heart in the higher vertebrates.
      (b) In the lower vertebrates, a distinct chamber of the
          heart formed by the union of the large systematic
          veins and opening into the auricle.
          [1913 Webster]
    

48 Moby Thesaurus words for "sinus":
      alveolation, alveolus, antrum, arc, armpit, basin, bow, bowl,
      catacaustic, catenary, caustic, cavity, circle, concave, concavity,
      conchoid, crater, crook, crypt, cup, curl, curve, depression,
      diacaustic, dip, ellipse, festoon, fold, follicle, funnel chest,
      hole, hollow, hollow shell, hook, hyperbola, lacuna, lituus,
      parabola, pit, pocket, punch bowl, scoop, shell, sink, socket,
      tracery, trough, vug