A more thorough explanation:

Definition: Cats and dogs is a slang term used in the world of finance to describe nonperforming or highly speculative securities. It refers to low-priced, often worthless, speculative securities that are not expected to perform well.

For example, penny stocks are often considered cats and dogs because they are low-priced and highly speculative. The term dog can also be used to describe a worthless security, while pup was used in the past to describe a low-priced, inactive stock.

These examples illustrate how the term cats and dogs is used to describe securities that are not expected to perform well and are considered risky investments.