- The definition of vigilant is watchful and alert.
An example of something vigilant is a guard dog.
Origin: Fr from Classical Latin vigilans, present participle of vigilare, to watch from vigil, awake: see vigil
- vigilantly adverb
Used by arrangement with John Wiley & Sons, Inc.
Origin: Middle English, from Old French, from Latin vigilāns, vigilant-, present participle of vigilāre, to be watchful; see vigilante.
- vigˈi·lant·ly adverb