What does "immaculate" mean?

Immaculate: Without stain or blemish; spotless; undefiled; clear; pure. Were but my soul as pure From other guilt as that, Heaven did not hold One more immaculate. Denham. Thou sheer, immaculate and silver fountain. Shak. Immaculate conception (R. C. Ch.), the doctrine that the Virgin Mary was conceived without original sin. -- Im*mac"u*late*ly, adv. -- Im*mac"u*late*ness, n.