keenly watchful to detect danger; wary: a vigilant sentry.
ever awake and alert; sleeplessly watchful.
Origin of vigilant
Synonyms for vigilant
2. See alert.
Antonyms for vigilant
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
keenly alert to or heedful of trouble or danger, as while others are sleeping or unsuspicious
Word Origin for vigilant
C15: from Latin vigilāns keeping awake, from vigilāre to be watchful; see vigil
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
late 15c., from Latin vigilantia "wakefulness," from vigilia (see vigil). Related: Vigilantly.
Online Etymology Dictionary, © 2010 Douglas Harper