1. Kept secret
   "the plan was kept carefully under wraps"

See also: covert

• markhor
• marking
• marking ink
• markka
• Markoff chain
• Markoff process
• Markov
• Markov chain
• Markov process
• Markova
• Markovian
• Marks
• marksman
• marksmanship
• markup
• markup language
• markweed
• marl
• marlberry
• Marlene Dietrich
• Marley
• marlin
• marline
• marlinespike
• marlingspike