Ebullient means bursting with energy, excitement, and cheerfulness. When someone is ebullient, they're so full of enthusiasm that it practically bubbles over and spreads to everyone around them.

Picture a student who just found out she made the basketball team, bouncing down the hallway with a huge smile, high-fiving everyone she passes, and talking a mile a minute about the first practice. That's ebullience in action. Or imagine a scientist whose experiment finally worked after months of failures, laughing and practically dancing around the laboratory while explaining the breakthrough to anyone who will listen.

Ebullient people radiate joy and energy. Their enthusiasm is contagious: when an ebullient friend shares good news, you can't help but feel excited, too.

You might describe someone's ebullient personality, or say they gave an ebullient performance. The related noun is ebullience: “Her ebullience was infectious, making everyone at the party feel more energetic and happy.”