Define Sexual penetration. Sexual penetration synonyms, Sexual penetration pronunciation, Sexual penetration translation, English dictionary definition of Sexual penetration. n. 1. Sexual union between a male and a female involving insertion of the penis into the vagina. 2. Sexual activity that includes insertion of the penis... Penetration (firestop), an opening in a wall or floor assembly required to have a fire-resistance rating, for the purpose of accommodating the passage of a mechanical, electrical, or structural penetrant The meaning of PENETRATION is the power to penetrate; especially : the ability to discern deeply and acutely. How to use penetration in a sentence. Synonym Discussion of Penetration. Penetration testing, or pen testing, is a practice where a simulated cyber attack is conducted on your computer systems to find and fix any weak spots before real attackers can exploit them. It focuses on web application security, where testers try to breach parts like APIs and servers to uncover vulnerabilities such as code injection risks from unfiltered inputs. The results help adjust web application firewall (WAF) settings and fix any weaknesses found to boost overall security ...