Answer:
Round as an apple, deep as a cup, and all the kings' horses can't fill it up. What is it?
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. The wind is my lover, one-legged am I. Name me and see me at home in the sky.
Just head and foot yet never tires of dancing.
My first is high, My second damp, My whole a tie, A writer's cramp
Three little letters. A paradox to some. The worse that it is, the better it becomes.
You use it between your head and your toes, the more it works the thinner it grows.