Klaxon, Mayday, Sos, Active, Admonish, Advise, Agile, Agog, Alarm, Alive, Animated, Apt, Arouse, Assiduous, Attentive, Awake, Aware, Beacon, Brainy, Breathe, Bright, Brilliant, Buzz, Buzzer, Cant, Careful, Caution, Cautious, Clearheaded, Clever, Concentrated, Confide, Conscious, Decisive, Diligent, Earnest, Expeditious, Finicky, Foghorn, Forewarn, Frighten, Frisky, Gay, Heedful, Hooter, Horn, Immediate, Instant, Instantaneous, Intense, Intent, Keen, Knowing, Lighthouse, Lively, Lookout, Mercurial, Meticulous, Mindful, Nice, Niggling, Nimble, Notify, Observant, Observing, Prompt, Punctual, Quick, Ready, Sharp, Signal, Siren, Sleepless, Smart, Speedy, Spirited, Sprightly, Spry, Startle, Summary, Swift, Threaten, Tip, Tocsin, Unblinking, Up, Vigilant, Vivacious, Wakeful, Warn, Warning, Wary, Watchful, Whisper, Whistle