Allegro
/əˈleɪɡɹoʊ/
noun
A tempo mark directing that a passage is to be played in a quick, lively tempo, faster than allegretto but slower than presto
In more traditional use, an expressive marking indicating lively or happily, not necessarily quick or fast.
A passage having this mark
adjective
In a quick and lively manner
adverb
Played in a quick, lively tempo