Stumpy describes something short and thick, like it's been cut off or is naturally stubby. A stumpy pencil has been sharpened so many times it's barely long enough to hold. A stumpy tail on a dog might be naturally short and thick.

You might describe a person's fingers as stumpy if they're shorter and thicker than usual, or call someone's legs stumpy if they're noticeably short compared to their body. A stumpy candle has burned down to a small, thick stub. The word is mainly descriptive: it points out that something is shorter and stubbier than you'd normally expect.