The idiom "wild goose chase" refers to a task or activity that is fruitless, pointless or a waste of time. It is often used to describe an endeavor that involves searching for something that is unlikely to be found or achieving a goal that is unattainable.

The idiom "mean business" means to be serious, intentional, or earnest in one's actions or intentions. It implies a level of urgency or importance that requires immediate attention.

The idiom "no spring chicken" refers to someone who is old or experienced, rather than being young or inexperienced. It suggests that the person has lived through many experiences and knows what they're talking about.

The idiom "to the core" means to do something sincerely, deeply, or completely. It suggests that a person is being honest and genuine in their actions or words, and that they are not just putting on a show or pretending to be someone else.

The idiom "dog in the manger" refers to a person or thing that takes advantage of or exploits others. It originates from the story of a dog that steals food from a manger (a trough for feeding animals), leaving nothing for the actual owner of the food.