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

See also: wary

• skillfulness
• skilling
• skilly
• skim
• skim milk
• skim off
• skim over
• skimcoat
• skimmed
• skimmed milk
• skimmer
• skimming
• skimp
• skimp over
• skimpily
• skimpy
• skin
• skin and bones
• skin cancer
• skin cell
• skin color
• skin colour
• skin disease
• skin disorder
• skin diving