Real Dictionary

cadenza
countable noun: In classical music, a cadenza is a long and difficult solo passage in a piece for soloist and orchestra.

cadenza in American English
an elaborate, often improvised musical passage played unaccompanied by the solo instrument in a concerto, usually near the end of the first or the final movement
noun: an elaborate flourish or showy solo passage, sometimes improvised, introduced near the end of an aria or a movement of a concerto

cadenza in British English
noun: a virtuoso solo passage occurring near the end of a piece of music, formerly improvised by the soloist but now usually specially composed