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.
2. A bay of the sea; a recess in the
shore.
3. (Anat. &
Zoöl.) 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.
4. (Med.) A narrow, elongated cavity, in which pus
is collected; an elongated abscess with only a small orifice.
5. (Bot.) A depression between adjoining
lobes.
&fist; A sinus may be
rounded, as in the leaf of the white
oak, or acute, as in that of the red maple.
Pallial sinus.
(Zoöl.) 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.
Hear it pronounced