To be in a situation that you have not been in before.
The company just started manufacturing smartphones. These are uncharted waters for them.
Being criticized a lot.
He came under fire for his coaching decisions.
Under the Weather:
She’s under the weather today. I think she ate something bad.
Until the cows come home:
To do something for a very long time.
You can keep stalling until the cows come home. But you have to eventually start that essay.
Up in the air:
When something is unresolved or undecided.
My plans for the weekend are up in the air.
Up the ante:
To raise what is at stake.
My boss upped the ante when she told me I could either use the new system (which I disliked) or start looking for a new job.