noun.
A horse finger is just what it says it is: a horse's finger, but if you have ever seen a horse; you would know that horses have no fingers, and that horse fingers don't exist. Which is why it is used as an insult, because if you call someone a horse finger you're saying that they are essentially nothing.

a person who uses only two fingers (usually the indexes) to type. As a result, typing is haphazard and typos often occur. Using horsefingers is also accompanied by a 'tap tapping' similar to that of a horses shoes.