The Collaborative International Dictionary sestuor Sestet \Ses*tet"\, n. [It. sestetto, fr. sesto sixth, L. sextus, fr. sex six.] (Mus.) A piece of music composed for six voices or six instruments; a sextet; -- called also sestuor. [Written also sestett, sestette.] (Poet.) The last six lines of a sonnet. Wiktionary sestuor n. A sestet.