1. (n.) One who watches or guards; a soldier set to guard a camp\ from surprise, to observe the approach of danger, and give notice of it; a sentry.

2. (n.) Watch; guard.

3. (n.) A marine crab (Podophthalmus vigil) native of the Indian Ocean, remarkable for the great length of its eyestalks; -- called also sentinel crab.

4. (v. t.) To watch over like a sentinel.

5. (v. t.) To furnish with a sentinel; to place under the guard of a sentinel or sentinels.

Druid Eeyore Jeremiah admonisher astrologer augur calamity howler cautioner crepehanger crystal gazer cynic defeatist divinator diviner divineress flagman forecaster foreknower foreseer foreshower foreteller fortuneteller geomancer haruspex killjoy lighthouse keeper lookout lookout man malist monitor negativist nihilist palmist pessimist predictor prefigurer presager prognosticator prophesier prophet prophet of doom prophetess psychic pythoness religious prophets retreatist seek-sorrow seer seeress sentinel sentry signaler signalman soothsayer vates warner weather prophet worrywart