An exclamation of encouragement for someone who is about to participate in something, often a competition, that is intended to motivate them to give their maximum effort in order to defeat their opponent ("them") or achieve success within that arena. "Them" is often shortened to "'em" or "em." Good luck out there, Dara! Give them hell! A: "I just don't know if I'm cut out for college." B: "Nonsense! You're gonna give 'em hell!"