Synonyms and related words :
advertent, agile, agog, alert, alive, all ears, all eyes, assiduous, attentive, awake, aware, bright, careful, clear-sighted, clear-witted, clearheaded, concentrated, conscious, diligent, earnest, finical, finicking, finicky, heedful, intense, intent, intentive, keen, meticulous, mindful, nice, niggling, nimble, observant, observing, on the, on the alert, on the job, open-eared, open-eyed, openmouthed, prompt, qui vive, quick, ready, regardful, sharp, sleepless, smart, unblinking, unnodding, unsleeping, unwinking, wakeful, watchful, wide-awake