1. Vigilant
   - on guard, upon one's guard, on your guard

See also: wary

• Amos
• amount
• amount of money
• amour
• amour propre
• amoxicillin
• Amoxil
• Amoy
• amp
• amperage
• ampere
• ampere-hour
• ampere-minute
• ampere-second
• ampere-turn
• ampersand
• amphetamine
• amphetamine sulfate
• amphetamine sulphate
• amphibia
• amphibian
• amphibian family
• amphibian genus
• amphibiotic
• amphibious