sentinel

UK: /ˈsɛntɪn^əl/ US: /ˈsɛntənəl/ ,(sen′tn l)

Inflections of 'sentinel' (v): (⇒ conjugate)

When both "l" and "ll" forms exist, spellings with a double "l" are correct, but rare, in US English, while those with a single "l" are not correct in UK English.

sentinels

v 3rd person singular

sentinelling

v pres p (Mainly UK)

sentineling

v pres p (US)

sentinelled

v past (Mainly UK)

sentineled

v past (US)

sentinelled

v past p (Mainly UK)

sentineled

v past p (US)

WordReference Random House Learner's Dictionary of American English © 2025

sen•ti•nel /ˈsɛntənəl/   n. [countable]

1. a person or thing that guards;
   sentry.

WordReference Random House Unabridged Dictionary of American English © 2025

sen•ti•nel  (sen′tn l), n., v., -neled, -nel•ing or (esp. Brit.) -nelled, -nel•ling. 
n. 

1. a person or thing that watches or stands as if watching.
2. Military a soldier stationed as a guard to challenge all comers and prevent a surprise attack:
   to stand sentinel.
3. Computing Also called tag. a symbol, mark, or other labeling device indicating the beginning or end of a unit of information.

v.t. 

4. to watch over or guard as a sentinel.

• Italian sentinella, derivative of Old Italian sentina vigilance (Latin sent(īre) to observe) + -īna -ine²)
• Middle French sentinelle
• 1570–80

sen′ti•nel•like′, adj. 
sen′ti•nel•ship′, n. 
Synonyms

• 1, 2. sentry, guard, watch, lookout.

Collins Concise English Dictionary © HarperCollins Publishers::

sentinel / ˈsɛntɪn^əl/ noun

1. a person, such as a sentry, assigned to keep guard

verb ( -nels, -nelling, -nelled) ( -nels, -neling, -neled)(transitive)

1. to guard as a sentinel
2. to post as a sentinel

Etymology: 16th Century: from Old French sentinelle, from Old Italian sentinella, from sentina watchfulness, from sentire to notice, from Latin