If someone is 'under the weather', how are they feeling?

What does 'Break the ice' mean?

What does the idiom 'Bite the bullet' mean?

What does 'Spill the beans' mean?

What is the meaning of 'Piece of cake'?

What does the phrase 'Barking up the wrong tree' mean?

If someone tells you to 'hit the sack', what should you do?