- 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."The sentinels who paced the ramparts." [Macaulay.]
- Watch; guard.(Obs)"That princes do keep due sentinel." [Bacon.]
- [Zoöl] A marine crab (Podophthalmus vigil) native of the Indian Ocean, remarkable for the great length of its eyestalks; -- called also sentinel crab.
Etymology: F. sentinellecf. It. sentinella); probably originally, a litle path, the sentinel's beat,, and a dim. of a word meaning, path; cf. F. sente path. L. semita; and OF. sentine sentele senteret, diminutive words. Cf. Sentry