1. Not prepared or vigilant
   - napping, off-guard, off guard, off one's guard, off his guard, off your guard

See also: unready

• mercury-in-glass thermometer
• mercury-vapor lamp
• mercury-vapour lamp
• mercy
• mercy killing
• mercy seat
• mere
• Meredith
• merely
• merengue
• merestone
• up-to-the-minute
• Upanishad
• upas
• upbeat
• upbound
• upbraid
• upbraider
• upbraiding
• upbringing
• upcast
• upchuck
• upcoming
• upcountry
• upcurved