1. United States prizefighter who won the world heavyweight championship three times (born in 1942) • Syn: Muhammad Ali, Cassius Clay, Cassius Marcellus Clay • Instance Hypernyms: prizefighter, gladiator 2. the fourth caliph of Islam who is considered to be the first caliph by Shiites; he was a cousin and son-in-law of Muhammad; after his assassination Islam was divided into Shiite and Sunnite sects • Instance Hypernyms: caliph, calif, kaliph, kalif, khalif, khalifah