R.C.Ch. the doctrine that the Virgin Mary, though conceived naturally, was from the moment of conception free from any original sin: sometimes confused with virgin birth
See Immaculate Conception in American Heritage Dictionary 4
(ĭ-măkˈyə-lĭt)
noun
Roman Catholic Church The doctrine that the Virgin Mary was conceived free from all stain of original sin.
December 8, on which the feast of the Immaculate Conception is celebrated.