Definition of sentinel :
1. A marine crab ( Podophthalmus vigil) native of the Indian Ocean, remarkable for the great length of its eyestalks; - called also sentinel crab.
2. 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.
3. To furnish with a sentinel; to place under the guard of a sentinel or sentinels.
4. To watch over like a sentinel.
5. Watch; guard.
ticker, gatekeeper, pale, outlook, doorkeeper, finder, beefeater, pathfinder, attack dog, caretaker, scout, awareness, lookout, talent scout, watchman, vigil, lookout man, piquet, sentry, ward, gamekeeper, watch, observatory, observation tower, observation post, protector, custodian, lookout station, spotter, guard, discoverer, safety, bodyguard, concierge, bruiser, picket, guide
- The sentinel ordered Boksa to wait there until the patrol came to lead him away.
- The Shawanoe looked at him intently for a moment as though he would read his thoughts, and then quietly said: " Deerfoot will be sentinel to- night!" - "The Hunters of the Ozark", Edward S. Ellis.
- Whether from ignorance of the country or of Mr. Gundry's plans, the sentinel had been posted badly. - "Erema My Father's Sin", R. D. Blackmore.