umpteenth

many, large number

Example:

Well, I have to go to the umpteenth meeting about the same old problem - falling profits.

under someone's thumb

under the control of someone

Example:

You like being under your wife's thumb, don't you?

under the weather

feeling ill

Example:

I feel a bit under the weather. Must have caught flu.

under wraps

in secret

Example:

The new product is under wraps. No-one knows what it is.

underwhelm

to not impress someone

Example:

His level of skill totally underwhelmed us.