Which term is primarily associated with a quick musical tempo?

The term "Allegro" is primarily associated with a quick musical tempo, typically indicating a brisk and lively pace. In musical terminology, allegro indicates speeds generally ranging from 120 to 168 beats per minute. It is often used in compositions to convey a sense of joyfulness and energy, encouraging a fast and spirited performance.

In contrast, the other terms have different implications in relation to tempo. "Molto" means "very" and is often used to modify other terms, suggesting an emphasis rather than indicating a tempo on its own. "Moderato" denotes a moderate pace, slower than allegro but faster than adagio, and it suggests a relaxed tempo. "Poco," meaning "a little," usually modifies other terms to indicate a slight degree of something, but does not specify tempo primarily associated with speed. Thus, "Allegro" stands out as the term that directly refers to a quick tempo.