Písale (PEE-sah-leh) literally means "step on it." As in English, it is used to make somebody hurry up. For more emphasis, it is usually followed by cabrón. Note: elongating the "o" in cabrón renders an even more desperate tone.
Pancho: ¿Qué? ¿Vamos a echar taco?
Poncho: Pero písale cabrón, que me estoy meando.
Pancho: Pérate. No mames.
Pancho: So, shall grab a bite?
Poncho: Just step on the gas, dude--I'm about to pee.
Pancho: Wait, wait. Don't fuck with me.