When you refer to your other intimate moments with your partner as first, second or third base, yet you have forgotten that the next step is referred to as a "home run", and is not called "fourth base". Yes, fourth base is sex, but come on! Just call it a home run! All the other bases are used in a reference to the bases is baseball. Have you ever played baseball? There's no fourth base!
"Dude, I totally got to fourth base with my girlfriend last night"

"You mean a 'home run'?"
"Yeah, either way we totally smashed".
by slurpeesaredelicous January 8, 2017
This is the final step in a relationship that involves having sex.
Me and Jace hit fourth base last night, oh boy was I ready for that.
by NekoNeoNano June 27, 2015
Means your home or your primary place of residence. The term is derived from Baseball where the Fourth Base in a diamond is called the 'Home Plate'...
"Ayo, holla at me, I'm at my fourth base dog"
by AdoubleR September 23, 2008
The final stage in a relationship that involves sexual intercourse.

First Base -- Making Out (tongue included)
Second Base -- Rubbing, Dry Humping, grinding.
Third Base -- Oral Sex
Fourth Base -- Sex
"I can't believe it, he got to fourth base on his first date with her!"
by Cloud Infinity December 21, 2006
first base: kissing/grinding
second base: blowjob
third base: sex
fourth base: anal
by xkeymastrx January 29, 2017
After 3ed base is when you add animals in your sexual activity.
"Jan and John throw butter and smokey in there titty fucking asshole pleasures when they got to fourth bases."
by dickinyourmouth January 23, 2009