1. Vigilant
   "on guard against con artists"
   - on one's guard, upon one's guard, on your guard

See also: wary

• productiveness
• productivity
• proem
• proemial
• proenzyme
• prof
• profanation
• profanatory
• profane
• profaned
• profanely
• profaneness
• profaner
• profanity
• profess
• professed
• professedly
• professing
• profession
• professional
• professional association
• professional baseball
• professional basketball
• professional boxing
• professional dancer