Which of these terms indicates a musical performance that is full of expression?

The term "Espressivo" is specifically used in music to indicate that a performance should be delivered with expression and emotion. When a composer includes this instruction in a score, it signals to the performer to infuse their interpretation with feelings, emphasizing dynamics, phrasing, and articulation to convey the intended emotions of the piece.

This contrasts with the other options, which denote different musical qualities. "Tranquillo," for instance, conveys a sense of tranquility or calmness but does not explicitly call for expressive playing. "Leggiero" refers to a light and nimble manner, suggesting a quick and delicate touch rather than emotional depth. "Vivace," on the other hand, indicates a lively and brisk pace, focusing on tempo rather than expression. Thus, "Espressivo" stands out as the term that emphasizes the importance of conveying feelings through music.