on someone's ass

Prepositional phrase

 * 1)  Rapidly chasing or pursuing someone.
 * 2)  Persistently urging someone on and putting pressure on them.
 * 1)  Persistently urging someone on and putting pressure on them.
 * 1)  Persistently urging someone on and putting pressure on them.

Usage notes

 * The term is usually considered disrespectful and contemptuous in formal settings, but is often used positively in informal settings.