mar·i·po·sa lily (mār'ə-pō'zə, -sə) n. Any of several bulbous plants of the genus Calochortus of western North America, having variously colored, tuliplike flowers. Also called mariposa tulip.
[Probably from American Spanish mariposa, from Spanish, butterfly, from María pósate, Mary alight!, María, Mary + pósate, second person sing. reflexive imperative of posar, to perch (from Late Latin pausāre, to pause, from Latin pausa, pause).]