SEMICIRCLE. A figure comprehended between the diameter of a circle and half the circumference.
SEMI-DIAMETER. The angle subtended by half the diameter of a heavenly body; in the cases of the sun and moon it is much used in navigation.
SEMI-DIURNAL ARC. Half the arc described by a heavenly body between its rising and setting.
SEMI-ISLET. An old term for [bridge-islet] (which see).
SEND, To. To rise after pitching heavily and suddenly between two waves, or out of the trough of the sea.
SENDING, or 'Scending. The act of being thrown about violently when adrift.
SENIORITY. The difference of rank, or standing in priority, according to dates of commissions; or if on the same day, the order in which they stand on the official printed lists.
SENIOR OFFICER. The commanding officer for the time being.
SENNIT. A flat cordage formed by plaiting five or seven rope-yarns together. Straw, plaited in the same way for hats, is called plat-sennit; it is made by sailors in India from the leaf of the palm, for that well-known straw-hat, adorned with flowing ribbons, which formerly distinguished the man-of-war's man.
SENSIBLE HORIZON. See [Horizon].