canon cancrizans
/ˈkaŋkrɪˌzanz
/noun Music
A canon in which the theme or subject is repeated backwards in the second part. Also called crab canon.In the 14th and 15th centuries, retrograde motion was employed to form what is known as crab canon, or canon cancrizans, wherein the original melody is turned backward to become the second voice.
Origin
Late 19th century: from canon1 + medieval Latin cancrizans 'walking backwards' (from cancer 'crab').