Depending on context, here are synonyms for "cat":
Formal
* Feline: The scientific and formal term.
* Catidae: The scientific family name.
Informal
* Kitty: Affectionate and common.
* Pussycat: Playful, though somewhat dated.
* Moggy: British slang for a domestic cat.
* Tabby: Refers to a striped coat pattern.
Archaic
* Frisk: Rare, poetic term.
* Grimalkin: Old-fashioned, often negative.