penetration
Pronunciation: /pɛnɪˈtreɪʃ(ə)n/
noun
- 1the action or process of penetrating something: the zip has a Velcro-secured flap to minimize rain penetration
- the insertion by a man of his penis into the vagina or anus of a sexual partner.

Origin:
late Middle English: from Latin penetratio(n-), from the verb penetrare 'place within or enter'