sentinel

1 of 2

noun

sen·​ti·​nel ˈsent-nəl 

ˈsen-tə-nəl

: sentry

sentinel

2 of 2

verb

sentineled or sentinelled; sentineling or sentinelling

transitive verb

1

: to watch over as a sentinel

2

: to furnish with a sentinel

3

: to post as sentinel

Synonyms

Noun

• guardian
• guard
• custodian
• warden
• keeper
• sentry

Examples of sentinel in a Sentence

Noun

a lone sentinel kept watch over the fort

Recent Examples on the Web

Noun

There’s another important way that dogs can benefit the study of cancer—as environmental sentinels. —Knowable Magazine, Smithsonian Magazine, 16 July 2025

Mutu plants her bronze figures in the gardens like sentinels from another world. —Lee Sharrock, Forbes.com, 30 June 2025

Verb

Since the outbreak was first reported in a Texas dairy herd last March, dead barn cats have served as sentinel warnings to veterinarians and investigators of the virus’ presence on a farm. —Susanne Rust, Los Angeles Times, 18 Jan. 2025

While penicillin was a game-changer, microorganisms were able to quickly adapt developing mutations to neutralize the effects of this antibiotic, sort of like those robot sentinels in the movie X-Men: Days of Future Past. —Bruce Y. Lee, Forbes, 17 Sep. 2024

Word History

Etymology

Noun

Middle French sentinelle, from Old Italian sentinella, from sentina vigilance, from sentire to perceive, from Latin

First Known Use

Noun

1579, in the meaning defined above

Verb

1593, in the meaning defined at sense 1

Phrases Containing sentinel

• stand sentinel

Rhymes for sentinel

• dentinal

Kids Definition

sentinel

noun

sen·​ti·​nel

ˈsent-(ə-)nəl

: sentry

Medical Definition

sentinel

adjective

sen·​ti·​nel ˈsent-ᵊn-əl 

: being an individual or part of a population potentially susceptible to an infection or infestation that is being monitored for the appearance or recurrence of the causative pathogen or parasite