penetration
n. the entry of the penis into the vagina. In the United States, legal definitions in cases of rape or illicit intercourse vary from state to state, but penetration is generally considered to have occurred if the glans penis passes beyond the labia majora. In some states, if penetration has not occurred during sexual assault, there cannot be a charge of rape. In such cases, the crime is some variety of felonious sexual assault, which usually has lower penalties than rape.