up in the air Share definition Flag adj. Something which is tentative, iffy, uncertain, unresolved, or otherwise not definitive. An unsettled matter. After George had that cold, the trip to the opera was completely up in the air. up in the air by united spammers January 13, 2011 0 0 Get merch Get the up in the air mug. Buy Now — $32.95 See more merch