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

See also: wary

• Megachile
• Megachilidae
• Megachiroptera
• megacolon
• megacycle
• megacycle per second
• megadeath
• Megaderma
• Megaderma lyra
• Megadermatidae
• Megaera
• megaflop
• megagametophyte
• megahertz
• megahit
• megakaryocyte
• megakaryocytic
• megalith
• megalithic
• megalithic structure
• megalo-
• Megalobatrachus
• Megalobatrachus maximus
• megaloblast
• megaloblastic