It refers to the conception of Mary as being without Original Sin.

它是指玛利亚的怀孕,圣洁无原罪。

耶鲁公开课 - 新约课程节选

My name is Maria D'Itria, and I teach 5th grade class at the Harvard Kent School in Boston.

我叫玛利亚。狄翠娅,我在波士顿的哈佛肯特学校教授五年级课程。

麻省理工公开课 - 媒体、教育、市场课程节选

Student: Mary's conception.

学生：玛利亚的怀孕。

耶鲁公开课 - 新约课程节选