Definition - What does Fourth Base mean?
Fourth base is the final step in a physical relationship referring to penetrative intercourse. Fourth base is also referred to as home or a home run.
Kinkly explains Fourth Base
The four bases are commonly used to describe what type of physical action a couple has together. Generally, first base refers to making out. Second base is rubbing, dry humping, and grinding. Third base is oral sex. Fourth base is penetrative intercourse.