sentinel

Meanings

Noun

• A sentry, watch, or guard.
• A private soldier.
• a unique string of characters recognised by a computer program for processing in a special way; a keyword.
• A sentinel crab.
• A sign of a health risk (e.g. a disease, an adverse effect).

Verb

• To watch over as a guard.
• To post as guard.
• To post a guard for.

Origin

• 1570s, from Middle French sentinelle, from Old Italian sentinella (perhaps via a notion of "perceive, watch", compare Italian sentire ("to feel, hear, smell")), from Latin sentiō. See sense.