They don't. They jump higher and further because they are stronger and better at doing so, not because they can resist gravity.
Gravity is not "used". In gymnastics, gymnasts almost defy-gravity by flipping in the air but have no control of what gravity does.
It doesn't, nothing can defy gravity.
No
yes
The plural of defy is defies. As in "this defies the laws of gravity".
The chemical that is called defying gravity.
Ultimately, no.
No they don't.
adhesion.
They cannot.
The water seemed to defy gravity.
No, they don't.