The term "old cat" can be substituted with a number of different phrases to convey the same meaning. Some synonyms for "old cat" include "mature feline," "senior kitty," "aged tabby," "elderly tom," and "veteran cat." These phrases can be used to describe a cat that has reached an advanced age and may have health issues that require special care. Another way to describe an "old cat" is to use terms like "wise," "experienced," and "grizzled," which highlight the cat's age and the knowledge they have gained over the years. Whatever phrase is used, it is important to remember that old cats still have a lot of love and affection to give and should be treated with respect and care.