sestuor
Webster's Dictionary (GCIDE)
Sestuor \Ses"tu*or\, n. [F.] A sestet. [1913 Webster]
Sestet \Ses*tet"\, n. [It. sestetto, fr. sesto sixth, L. sextus, fr. sex six.]
1.(Mus.) A piece of music composed for six voices or six instruments; a sextet; -- called also sestuor. [Written also sestett, sestette.] [1913 Webster]
2.(Poet.) The last six lines of a sonnet. [1913 Webster]