·noun Watch; guard.
II. Sentinel ·vt To watch over like a sentinel.
III. Sentinel ·vt To furnish with a sentinel; to place under the guard of a sentinel or sentinels.
IV. Sentinel ·noun A marine crab (Podophthalmus vigil) native of the Indian Ocean, remarkable for the great length of its eyestalks;
— called also sentinel crab.
V. Sentinel ·noun One who watches or guards; specifically (Mil.), a soldier set to guard an army, camp, or other place, from surprise, to observe the approach of danger, and give notice of it; a sentry.