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Definitions

on the lookout

ADJECTIVE
alert
Synonyms
STRONGEST
active bright careful intelligent observant perceptive sharp vigilant wary watchful wired wise
STRONG
hip jazzed quick ready spirited
WEAK
all ears cagey circumspect clever fast on the draw good hands heads up heedful on guard on one's toes on the ball on the job on the qui vive psyched-up switched on wide-awake with it
Antonyms
STRONGEST
careless dull foolish ignorant inattentive incautious indifferent indiscreet lazy negligent stupid thoughtless unaware unintelligent unobservant
STRONG
slow uneducated
WEAK
asleep drowsy lethargic sluggish weary
ADJECTIVE
attentive
Synonyms
STRONGEST
aware conscientious interested observant vigilant watchful
STRONG
heedful
WEAK
alert all ears awake enrapt enthralled fascinated glued hanging on every word hooked immersed intent listening mindful on one's toes on the ball on the job on the qui vive preoccupied regardful studious
Antonyms
STRONGEST
careless inattentive negligent unaware
WEAK
disregarding heedless ignorant inconsiderate neglectful neglecting unattentive
ADJECTIVE
cautious
Synonyms
STRONGEST
circumspect discreet judicious leery prudent tentative vigilant wary watchful
STRONG
alert safe
WEAK
all ears cagey calculating chary considerate forethoughtful gingerly hedging one's bets heedful keeping on one's toes playing it cool playing safe politic provident pussyfoot shrewd taking it easy taking it slow thinking twice walking on eggs watching one's step watching out with one's eyes peeled
Antonyms
STRONGEST
careless certain foolish inattentive incautious indiscreet negligent rash reckless sure thoughtless uncareful unwise
WEAK
hasty heedless imprudent unguarded unobservant
ADJECTIVE
guarded
Synonyms
STRONGEST
cautious circumspect reserved restrained
STRONG
calculating
WEAK
attentive cagey canny careful chary discreet gingerly leery noncommittal overcareful overcautious prudent reticent safe vigilant wary watchful with eyes peeled
Antonyms
STRONGEST
bold careless extroverted incautious outgoing rash uncareful
WEAK
unguarded unsuspicious unwatchful
ADJECTIVE
on one's guard
Synonyms
WEAK
alert careful cautious defensive guarded heedful mindful observant on guard on one's toes on the watch upon one's guard vigilant watchful
ADJECTIVE
on the ball
Synonyms
WEAK
active all ears attentive bright cagey careful clever good hands heads up intelligent lively observant on guard on one's toes on the job on the stick perceptive quick ready sharp spirited vigilant watchful wise with it
ADJECTIVE
open-eyed
Synonyms
WEAK
active all ears bright cagey careful circumspect clever fast on the draw good hands heads up heedful hip intelligent jazzed observant on guard on one's toes on the ball on the job on the qui vive perceptive psyched-up quick ready sharp spirited switched on vigilant wakeful wary watchful wide-awake wired wise with it
ADJECTIVE
politic
Synonyms
WEAK
adroit advisable canny cool delicate diplomatic discreet expedient in one's best interests judicious perspicacious prudent sagacious sensible sharp shrewd smooth tactical tuned-in urbane
Antonyms
WEAK
impolitic indiscreet injudicious tactless unwise
ADJECTIVE
unsleeping
Synonyms
WEAK
alive astir attentive awake careful heedful insomniac insomnious observant on guard on the alert on the qui vive sleepless vigilant waking wary watchful wide-awake
ADJECTIVE
vigilant
Synonyms
STRONGEST
anxious attentive aware cautious circumspect keen observant wary
WEAK
acute agog alert guarded looking for looking to on alert on guard on the ball on the job on the qui vive on toes open-eyed sharp sleepless unsleeping waiting on wakeful wide-awake with eyes peeled with weather eye open
Antonyms
STRONGEST
careless heedless ignorant inattentive incautious indifferent indiscreet rash thoughtless unaware uncareful unobservant
WEAK
impulsive negligent
ADJECTIVE
wakeful
Synonyms
WEAK
alive astir attentive careful heedful insomniac insomnious observant on guard on the alert on the qui vive sleepless unsleeping vigilant waking wary watchful wide-awake
Antonyms
WEAK
sleepy unaware
ADJECTIVE
wary
Synonyms
STRONGEST
attentive circumspect considerate distrustful frugal leery prudent suspicious vigilant watchful
WEAK
alert cagey calculating canny chary discreet doubting gingerly guarded handling with kid gloves heedful keeping on one's toes on guard on the qui vive provident safe saving sly sparing thinking twice thrifty unwasteful walking on eggs watching one's step watching out wide-awake
Antonyms
STRONGEST
careless certain inattentive incautious inconsiderate indiscreet negligent
WEAK
foolish heedless rash reckless
ADJECTIVE
wide-awake
Synonyms
WEAK
active alert all ears attentive bright bright-eyed and bushy-tailed fast on the draw heads up intelligent lively on guard on one's toes on the ball on the job psyched-up quick ready sharp spirited vigilant watchful wide-eyed wired
ADVERB
on guard
Synonyms
WEAK
alert careful cautious defensive guarded heedful mindful observant on one's guard on one's toes on the watch vigilant wary watchful

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Last quarter, the Gemini app had over 750 million monthly active users, and investors will be on the lookout for more signs of increased adoption in the beginning of 2026.

From MarketWatch • Apr. 28, 2026

Just be on the lookout in case your device or browser needs your permission to update and reboot.

From The Wall Street Journal • Apr. 19, 2026

Be on the lookout for a giant shovel.

From Los Angeles Times • Apr. 10, 2026

They will also be on the lookout for possible flashes of light caused by meteorites crashing into the surface of the Moon.

From Barron's • Apr. 5, 2026

Blake's handlers inside the KGB went to great lengths to shield him from MI6's counterespionage teams, who were always on the lookout for traitors and double agents within their ranks.

From "Spies: The Secret Showdown Between America and Russia" by Marc Favreau