1. (a.) Watchful; vigilant; active in vigilance.

2. (a.) Brisk; nimble; moving with celerity.

3. (n.) An alarm from a real or threatened attack; a sudden attack; also, a bugle sound to give warning.

Klaxon Mayday SOS active admonish advertent advise agile agog air-raid alarm alarm alarm bell alarm clock alarm signal alarum alert for alive all clear all ears all eyes animated apt arouse assiduous attentive awake aware beacon blinking light brainy breathe bright brilliant burglar alarm buzz buzzer cant careful caution cautious clear-sighted clear-witted clearheaded clever concentrated confide confide to conscious crostarie cry havoc cry wolf decisive diligent earnest entrust with information equal to expeditious fiery cross finical finicking finicky fire alarm fire bell fire flag five-minute gun flashing light fly storm warnings fog bell fog signal foghorn forewarn frighten frisky full of life gale warning gay give confidential information give fair warning give notice give warning heedful hooter horn hue and cry hurricane warning immediate instant instantaneous intense intent intentive issue an ultimatum keen knowing let in on let next to lighthouse lively loaded for lookout mention privately mercurial meticulous mindful nice niggling nimble note of alarm notify observant observing occulting light on guard on the on the alert on the ball on the job on the lookout open-eared open-eyed openmouthed police whistle prepared for prompt punctual put hep put next to qui vive quick quick-witted ready ready for regardful sharp signal signal of distress siren sleepless small-craft warning smart sound the alarm sound the tocsin speedy spirited sprightly spry startle still alarm storm cone storm flag storm warning summary swift threaten tip tip off tocsin two-minute gun unblinking unnodding unsleeping unwinking up up for up to upside-down flag utter a caveat vigilant vivacious wakeful warn warn against warning wary watchful whisper whistle wide awake wide-awake