What does the expression "up in the air" mean?

as in, "tommorow is up in the air"

if anyone does answer, thank you for taking the time to do so... even though i'm young, i still seem to lack knowledge for all the terms people my age use.. sad eh?

 

It means not knowing, nothing is set or for sure so its up in the air.

 

1. very uncertain;
2. not yet determined;

(I apologize if PeaceKeeper already answered this making my post redundant. I have him on ignore)

 

up in the air

Not settled, uncertain, as in The proposal to build a golf course next to the airport is still up in the air. This metaphoric expression likens something floating in the air to an unsettled matter. Put as in the air from the mid-1700s, it acquired up in the first half of the 1900s.

 

thanks