Archaic 1920s American slang that in various contexts refers to one or more of "excellent", "stylish", or "impressive to the ladies".
Synonymous with the cat's pyjamas and the bees' knees.
George, your zoot suit is quite thecat's meow! Perhaps now you will have a chance of capturing the attention of that flapper Matilda, she of the crimson ankle-baring swimsuit!