A bird with a sharp tail.
People might think of the bird as having a dangerous or interesting tail.
Examples:
The sharptail is a bird with a sharp tail.
I saw a sharptail in the forest.
The sharptail's tail is very sharp.
The sharptail's tail is so sharp, it can cut things!
The sharptail's tail is the sharpest in the world.
The sharptail's tail is as sharp as a knife.