What does the term "ebullience" best describe?

The term "ebullience" refers to a state of being enthusiastic and full of energy, often marked by lively expressions and exuberance. This concept encapsulates a sense of overflowing joy or excitement, making "overflowing with enthusiasm" the best description of its meaning. In contexts where ebullience is present, one might observe spirited behavior, lively conversation, and a general sense of positivity and vigor.

On the other hand, the other choices reflect contrasting emotional states or characteristics. A calm and reserved demeanor is the opposite of the energetic expression that defines ebullience. Similarly, extreme sadness or sorrow and indifference to emotions both signify a lack of enthusiasm, which does not align with the concept of being ebullient. Therefore, the choice that most accurately captures the essence of the term is indeed the one indicating overflowing enthusiasm.