What does "immaculate conception" mean?

Any virgin birth or an event likened to one.

Immaculate conception

Common synonyms include: december 8, dei mater, deipara, holy mary, immaculate conception of the virgin mary, madonna.

name, noun, slang

name, noun, slang ·Moderate ·College level

Noun

1
Any virgin birth or an event likened to one. informal, lowercase, often, proscribed, uncountable
"I didn't think the cat had gotten out, but either she did or those kittens are a case of immaculate conception."
2
(Christianity) the Roman Catholic dogma that God preserved the Virgin Mary from any stain of original sin from the moment she was conceived wordnet
3
Roman Catholic holy day first celebrated in 1854 wordnet

Proper Noun

1
The doctrine, in the Roman Catholic Church, that the Virgin Mary was conceived biologically but free from original sin.
2
December 8th (The Feast of the Immaculate Conception of Mary).
3
The conception or incarnation of Jesus as viewed by those who believe that he was conceived without sin. proscribed
4
A title of Mary, in particular reference to her unique status with regard to the aforementioned doctrine.

"I didn't think the cat had gotten out, but either she did or those kittens are a case of immaculate conception."