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

See also: wary

• ordered
• ordered series
• orderer
• ordering
• orderliness
• orderly
• orderly sergeant
• ordinal
• ordinal number
• ordinance
• ordinand
• ordinarily
• ordinariness
• ordinary
• ordinary annuity
• ordinary bicycle
• ordinary care
• ordinary life insurance
• ordinary seaman
• ordinary shares
• ordinate
• ordination
• ordnance
• ordnance store
• Ordnance Survey