ebullient (eh-BOOL-yunt), adj.
Full of cheer, enthusiasm, or optimism, as expressed in speech, writing, or behavior.
1. Zestfully enthusiastic.
2. Boiling or seeming to boil; bubbling.
Latin: ebuliere, to bubble up.
My professor was particularly ebullient when lecturing about Thomas Jefferson, his favorite president.
Some find my constant state of ebullience delightful, while others simply consider it annoying.
Isn't the 1st definition from American Heritage absolutely delicious? "Zestfully enthusiastic" is one of the happiest, most exuberant phrases I've ever read. The fact that it can be summed up into "ebullient" makes it even better.