1. Very uncertain
   "left everything up in the air" 
2. Not yet determined
   "plans are still up in the air"

See also: uncertain

• 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
• marlinspike
• marlite