The idiom "hard cheese" is used to express disbelief or shock when someone says something that you find unacceptable or offensive. It can also be used to express disappointment or frustration when someone does not fulfill your expectations.

The idiom "in stitches" means to be very happy, pleased or delighted with something. It can also mean being utterly amused by a situation or someone's behavior.

The idiom "castles in the air" means to plan or daydream about something grand or elaborate that is unlikely to happen in reality. It can also mean making promises or plans without any intention of fulfilling them.

The idiom "gut feeling" refers to an intuitive or instinctive sense of what is right or wrong, true or false, without any rational or logical explanation. It's a hunch or a sixth sense that can guide us in making decisions or predicting outcomes.

The idiom "brown study" means to be confused or puzzled, especially when trying to understand something. It can also mean to be in a state of bewilderment or disorientation.