Of or relating to any of the five popes named Sixtus, especially Sixtus IV (1414-1484; reigned 1471-1484) and Sixtus V (1520-1590; reigned 1585-1590).
Of or relating to the Sistine Chapel in the Vatican.
[Italian sistino, from New Latin sixtīnus, from Medieval Latin Sixtus, the name of several popes, from Latin Sextus, Roman praenomen, from sextus, sixth; see sext.]
1769, lit. "pertaining to Pope Sixtus," from It. sistino, from Sixtus, name of five popes, from L. sextus "sixth" (see Sextus). The "chapel" is named for Sixtus IV (Francesco della Rovere), pope 1471-84, who had it built.