WordWeight : Weighing the Words

Pronunciation : Si"nus, n.; pl. L. Sinus
Part of Speech : E.
Etymology : [L., a bent surface, a curve, the folds or bosom of a garment, etc., a bay. Cf. Sine, n.]
Definition : 1. An opening; a hollow; a bending.

2. A bay of the sea; a recess in the shore.

3. (Anat. & Zo?l.)

Defn: 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.)

Defn: A narrow, elongated cavity, in which pus is collected; an elongated abscess with only a small orifice.

5. (Bot.)

Defn: A depression between adjoining lobes.

Note: A sinus may be rounded, as in the leaf of the white oak, or acute, as in that of the red maple. Pallial sinus. (Zo?l.) See under Pallial. -- Sinus venosus. Etym: [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.

Sinuses.
Source : Webster's Unabridged Dictionary, 1913