1. Carefully observant or attentive; on the lookout for possible danger
   "the vigilant eye of the town watch"
   - argus-eyed, open-eyed, wakeful

See also: alert, vigilance, vigilantly, watchful

Encyclopedia: Vigilant

• operating instructions
• operating microscope
• operating procedure
• operating room
• operating statement
• operating surgeon
• operating system
• operating table
• operating theater
• operating theatre
• operation
• operation code
• Operation Desert Storm
• operational
• operational casualty
• operational cell
• operational damage
• operationalism
• operationalist
• operationally
• operations
• operations research
• operative
• operative field
• operatively