/ ˈvɪdʒɪlənt; NAmE / adjective
( formal ) very careful to notice any signs of danger or trouble
SYN alert , watchful :
A pilot must remain vigilant at all times.
► vigi·lance / -əns; NAmE / noun [ U ]
SYN watchfulness :
She stressed the need for constant vigilance.
► vigi·lant·ly adverb
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WORD ORIGIN
late 15th cent.: from Latin vigilant- keeping awake, from the verb vigilare , from vigil awake.