What musical term describes a strong and robust manner of playing?

The musical term "robusto" translates to a robust or strong manner of playing. It suggests that the performer should exude energy and confidence, typically implying a vigorous and powerful delivery of the music. This term is often used to instruct musicians to incorporate a certain vitality and fullness in their sound, which can enhance the emotional impact of the piece being performed.

The other terms do not represent a strong manner of playing. For instance, "con moto" refers to playing with movement, indicating a lively character but not necessarily a strong one. "Mordent" describes a specific kind of ornamentation in music rather than a style of playing, and "tranquillo" denotes a calm or tranquil manner, which contrasts with the assertive nature of "robusto." Therefore, "robusto" is the appropriate choice as it directly conveys the idea of strength and power in performance.