Music. an 18th-century instrumental suite for outdoor performance, similar to the divertimento and the serenade.
Origin: 1375–1425; late ME cassacio(u)n < ML cassātiōn- (s. of cassātiō), equiv. to LL cassāt(us) ptp. of cassāre to annul (cass- var. of L quass- (see quash) + -ātus-ate1) + -iōn--ion
[ka-sey-shuh
n, kuh-] 