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

See also: uncertain

• trend-setter
• trendily
• trendiness
• trendsetting
• trendy
• Trent
• Trent River
• Trental
• trente-et-quarante
• Trentino-Alto Adige
• Trento
• Trenton
• trepan
• trepang
• trephination
• trephine
• Trephritidae
• trepid
• trepidation
• trepidly
• treponema
• Treponemataceae
• trespass
• trespass de bonis asportatis
• trespass on the case