What is a short tailed weasel with long fur called?

A short-tailed weasel with long fur is called a long-tailed weasel (Mustela frenata).

It's a bit of a word trick! While they are called "long-tailed" weasels, they actually have shorter tails than their close relative, the short-tailed weasel (Mustela erminea). The term "long-tailed" refers to the fact that they don't have a distinct "ermine" coat, which is the white winter coat of the short-tailed weasel.